WO2014115322A1 - Negative electrode active material for lithium ion secondary cell, and lithium ion secondary cell obtained using same - Google Patents

Negative electrode active material for lithium ion secondary cell, and lithium ion secondary cell obtained using same Download PDF

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WO2014115322A1
WO2014115322A1 PCT/JP2013/051694 JP2013051694W WO2014115322A1 WO 2014115322 A1 WO2014115322 A1 WO 2014115322A1 JP 2013051694 W JP2013051694 W JP 2013051694W WO 2014115322 A1 WO2014115322 A1 WO 2014115322A1
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negative electrode
lithium ion
active material
ion secondary
electrode active
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PCT/JP2013/051694
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French (fr)
Japanese (ja)
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明秀 田中
西村　悦子
賢匠 星
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株式会社 日立製作所
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Priority to PCT/JP2013/051694 priority Critical patent/WO2014115322A1/en
Priority to JP2014558401A priority patent/JP5941999B2/en
Publication of WO2014115322A1 publication Critical patent/WO2014115322A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a negative electrode active material for a lithium ion secondary battery and a lithium ion secondary battery using them.
  • a lithium ion secondary battery having a high energy density is mainly used rather than a lead storage battery or a Ni-Cd battery.
  • the negative electrode active material When a carbon material capable of absorbing and desorbing lithium ions is used as the negative electrode active material, lithium ions are absorbed between the layers of the carbon material during charging, and therefore metallic lithium does not precipitate on the negative electrode, and dendrites The problem of internal short circuit can be avoided.
  • the positive electrode and the negative electrode may be in contact in the battery, and an internal short circuit may occur.
  • an internal short circuit occurs, a large current is concentrated at a portion where the positive electrode and the negative electrode are in contact with each other and heat is generated, and the temperature of the battery may be rapidly increased to cause ignition.
  • non-aqueous solvents are mainly used in the electrolyte solution of lithium ion secondary batteries. Therefore, even if overcharging, heating, or a short circuit occurs, the heat generation runaway state does not occur, and it is important to ensure the reliability so that the battery does not burst and ignite.
  • the positive and negative electrodes have a volume resistivity at 180 ° C. which is greater than that at ⁇ 20 ° C. to 60 ° C. It is disclosed to provide a conductive material that is five times or more. As a result, it is possible to suppress a rapid temperature rise due to the short circuit current.
  • JP 2011-76822 A discloses that the volume resistivity of the negative electrode active material layer is increased.
  • the shutdown mechanism in which the short circuit current can not be suppressed unless the temperature is high does not have an effect of moderating heat generation at normal temperature. Therefore, even if current can be made difficult to flow at 100 to 200 ° C. or less, sudden heat generation causes continuous heat generation if the temperature of the positive electrode, negative electrode or electrolyte reaches self-heating by then. There is a risk of thermal runaway.
  • an object of the present invention is to improve the reliability of a lithium ion secondary battery while suppressing an increase in battery resistance.
  • a negative electrode active material for a lithium ion secondary battery that absorbs and releases lithium ions wherein the negative electrode active material has a core material made of carbon, and has a volume resistivity of 0.32 ⁇ at a density of 2.0 g / cc.
  • r 2 is the volume resistivity in the density of 2.0 g / cc
  • r 1 represents the volume resistivity at a density 1.2 g / cc.
  • the negative electrode active material for lithium ion secondary batteries which improved the reliability of the lithium ion secondary battery can be provided, suppressing the raise of the resistance of a battery.
  • the effect of the battery after cycle deterioration is large.
  • process is included in the term if the intended function of the process is achieved, even if it can not be clearly distinguished from other processes, not only the independent process. .
  • a numerical range indicated using “to” indicates a range including numerical values described before and after “to” as the minimum value and the maximum value, respectively. All publications, patents and patent applications cited herein are incorporated herein by reference in their entirety.
  • FIG. 1 is a view schematically showing an internal structure of a battery according to an embodiment of the present invention.
  • a battery 1 according to an embodiment of the present invention shown in FIG. 1 includes a positive electrode 10, a separator 11, a negative electrode 12, a battery can 13, a positive current collecting tab 14, a negative current collecting tab 15, an inner lid 16, an internal pressure release valve 17, A gasket 18, a positive temperature coefficient (PTC) resistance element 19, a battery cover 20, and an axial center 21 are provided.
  • the battery lid 20 is an integrated component including the inner lid 16, the internal pressure release valve 17, the gasket 18, and the resistance element 19. Further, the positive electrode 10, the separator 11 and the negative electrode 12 are wound around the axial center 21.
  • the separator 11 is inserted between the positive electrode 10 and the negative electrode 12, and an electrode group wound around the axial center 21 is produced.
  • the shaft 21 any known one can be used as long as it can support the positive electrode 10, the separator 11 and the negative electrode 12.
  • the electrode group may be formed into various shapes, such as one obtained by laminating strip electrodes, or one obtained by winding the positive electrode 10 and the negative electrode 12 into an arbitrary shape such as flat.
  • the shape of the battery can 13 may be a cylindrical shape, a flat oval shape, a flat oval shape, a square shape, or the like in accordance with the shape of the electrode group.
  • the material of the battery can 13 is selected from materials having corrosion resistance to the non-aqueous electrolyte, such as aluminum, stainless steel, nickel plated steel, and the like. Moreover, when the battery can 13 is electrically connected to the positive electrode 10 or the negative electrode 12, the material of the battery can 13 does not deteriorate due to corrosion or alloying with lithium ions in a portion in contact with the non-aqueous electrolyte. Thus, the material of the battery case 13 is selected.
  • the electrode group is housed in the battery can 13, the negative electrode current collecting tab 15 is connected to the inner wall of the battery can 13, and the positive electrode current collecting tab 14 is connected to the bottom surface of the battery cover 20.
  • the electrolyte is injected into the inside of the battery can 13 before sealing the battery.
  • a method of injecting the electrolytic solution there is a method of adding directly to the electrode group in a state in which the battery cover 20 is released, or a method of adding from an injection port provided on the battery cover 20.
  • the battery cover 20 is brought into close contact with the battery can 13 to seal the entire battery. If there is an electrolyte inlet, seal it as well.
  • a method of sealing the battery there are known techniques such as welding and caulking.
  • the lithium ion secondary battery according to one embodiment of the present invention can be manufactured, for example, by arranging the following negative electrode and positive electrode as opposed to each other with the separator interposed therebetween, and injecting an electrolyte.
  • the structure of the lithium ion secondary battery according to one embodiment of the present invention is not particularly limited, but usually, the positive electrode and the negative electrode and the separator separating them are wound to form a wound electrode group, or the positive electrode, the negative electrode and The separators can be stacked to form a stacked electrode group.
  • the configuration of the battery shown in FIG. 1 is merely an example of the internal structure of a lithium ion secondary battery to which the negative electrode active material for a lithium ion secondary battery according to an embodiment of the present invention can be applied, and an embodiment of the present invention
  • the battery to which the negative electrode according to the present invention is applicable is not limited to the one described in FIG.
  • the volume resistivity in the state of low density of graphite is not large compared with the state of high density of graphite after cycle deterioration.
  • the volume resistivity at low density is large, the electron conductivity is lowered and the resistance of the battery is increased.
  • the effect of improving the reliability of the lithium ion secondary battery is also small.
  • the negative electrode active material of the present invention is a carbon material having a spacing of 0.334 nm to 0.338 nm between the carbon 002 planes determined by XRD measurement, and has a volume resistivity of 0.32 ⁇ ⁇ at a density of 2.0 g / cc. It is a carbon particle for lithium ion secondary battery negative electrodes characterized by not less than cm and satisfying the following formula (1).
  • Formula (1) r 2 0.10.13 ⁇ r 1 r 1 is volume resistivity with a density of 1.2 g / cc
  • r 2 is volume resistivity with a density of 2.0 g / cc
  • volume resistivity at a density of 2.0 g / cc is less than 0.32 ⁇ ⁇ cm, the reliability of the lithium ion secondary battery after cycle deterioration may be reduced.
  • the volume resistivity of 2.0 g / cc is preferably 0.33 ⁇ ⁇ cm or more, and more preferably 0.34 ⁇ ⁇ cm or more.
  • the initial resistance of the battery is increased, which is not preferable. preferably satisfying r 2 ⁇ 0.13 ⁇ r 1, it is further preferable to satisfy r 2 ⁇ 0.14 ⁇ r 1.
  • Examples of means for increasing the volume resistivity of the negative electrode include a method in which the surface of the carbon active material is adsorbed or coated with an inorganic substance such as an oxide or a nitride, or a polymer.
  • adsorption of the present invention represents physical adsorption.
  • the material to be adsorbed and coated be present on the surface of the graphite as uniformly, as smoothly as possible. In the case of non-uniformity, the decrease in volume resistivity when changing from low density to high density tends to be large.
  • the material to be adsorbed and coated is preferably a material which is less likely to be deformed, cut or disintegrated at high density.
  • the decrease in volume resistivity when changing from low density to high density tends to be large.
  • the material is preferably a material that is not alloyed with lithium ions.
  • a material to be alloyed with lithium ion is easily expanded by alloying, and when such a material is used, cycle characteristics may be deteriorated.
  • the material to be adsorbed and coated is preferably a nitride, and particularly a polymer among oxides and polymers.
  • a polymer it is because it is relatively inexpensive and easily adsorbed smoothly as compared with inorganic substances and oxides.
  • polyvinylsulfonic acid polyvinylsulfonic acid Na, polystyrenesulfonic acid, polystyrenesulfonic acid Na, polyacrylic acid, polyacrylic acid salt, polyacrylic acid ester, polymethacrylic acid, polymethacrylic acid salt, polymethacrylic acid An acid ester etc.
  • the weight average molecular weight of the polymer is preferably 10,000 to 1.2 million.
  • the above weight average molecular weight is a value measured by liquid chromatography.
  • the polymer is preferably a polymer of a monomer having a vinyl group or a styrene group as a polymerizable functional group.
  • the polymer is preferably a polymer of a monomer having an aromatic compound such as a styrene group rather than a vinyl group. It is because adsorption uniformity improves by making polarity high.
  • the polymer has a sulfur containing functional group.
  • a sulfur containing functional group a sulfonic acid group, a sulfonic acid group, a sulfonyl group, a thiol group, a sulfide group etc. are mentioned, for example.
  • These functional groups have high polarity, and the adsorption uniformity is improved.
  • One or more of these functional groups may be used as the sulfur-containing functional group.
  • the improved adsorption uniformity reduces the decrease in volume resistivity when changing from low density to high density.
  • those having a functional group as a salt are preferable.
  • it is an alkali metal salt, and Li, Na, K, Ca etc. can be mentioned as a counter ion.
  • Li and Na are particularly preferable.
  • the inorganic substance for coating the carbon surface eg CaO, Sc 2 O 3, SrO 2, SnO 2, BaO, La 2 O 3, Nd 2 O 3, WO 3, Al 2 O 3, oxides such as SiO 2 Or nitrides such as AlN, GaN, SiN, etc., or mixtures thereof.
  • a method of coating the carbon surface for example, using a coating method from a solution, a vapor deposition method, a Langmuir Blojet (LB) method, an electrolytic polymerization method, a plasma polymerization method, a CVD (chemical vapor deposition) method, a sputtering method Can.
  • the negative electrode 12 in an embodiment of the present invention includes the above-described negative electrode active material, a binder, and a current collector. When high rate charge and discharge are required, a conductive agent may be added.
  • Graphite can be selected as the negative electrode active material (nucleus material) to which the polymer usable in the embodiment of the present invention is adsorbed.
  • the graphite preferably has a graphite interlayer distance (d 002 ) of 0.334 nm or more and 0.338 nm or less. If it exceeds 0.338 nm, the capacity of the active material will be small, and the capacity of the battery will be small.
  • Graphite as the negative electrode active material is natural graphite capable of absorbing and desorbing lithium ions chemically, artificial graphite, mesophase carbon, expanded graphite, carbon fiber, vapor grown carbon fiber, pitch-based carbonaceous material, needle It is manufactured using coke, petroleum coke, polyacrylonitrile carbon fiber, etc. as a raw material.
  • the above-mentioned graphite interlayer distance (d 002 ) can be measured using XRD (X-Ray Diffraction Method) or the like.
  • the particle diameter of the negative electrode active material is desirably equal to or less than the thickness of the negative electrode mixture layer formed of the negative electrode active material and the binder. If the powder of the negative electrode active material contains coarse particles having a size greater than or equal to the layer thickness of the negative electrode mixture, the coarse particles are removed beforehand by sieve classification, air flow classification, etc., and particles smaller than the thickness of the negative electrode mixture layer are used. It is preferable to do.
  • the specific particle size is preferably 3 to 30 ⁇ m, more preferably 3 to 25 ⁇ m, particularly 5 to 20 ⁇ m, as determined by a laser diffraction / scattering particle size distribution analyzer. If the preferable average particle size exceeds 30 ⁇ m, the electrode characteristics may be easily uneven, and the battery characteristics may be deteriorated. Moreover, when it is less than 3 ⁇ m, since the graphite is hardly crushed, the density tends to be difficult to increase.
  • the particle size distribution can be measured by dispersing the sample in purified water containing a surfactant and using a laser diffraction / scattering type particle size distribution analyzer, and the average particle size is 50% cumulative (50% D). It is calculated.
  • the polymer to be adsorbed is preferably dissolved in pure water beforehand to be an aqueous solution from the viewpoint of enhancing the adsorption uniformity.
  • the method for producing the polymer aqueous solution is not particularly limited, but since the undissolved matter causes nonuniformity, it is necessary to be careful not to cause the undissolved matter. For example, it can be dissolved by adding little by little while stirring with a propeller or wave rotor. At this time, heat may be applied if necessary. In addition, filtration of the dissolved aqueous solution may be performed.
  • the concentration of the polymer aqueous solution is not particularly limited, but it is preferably about 0.5 to 2.0% by mass from the viewpoint of the undissolved matter. If the concentration is too low or too high, uniform adsorption will decrease.
  • the prepared polymer aqueous solution is added to the carbon material which is a negative electrode active material, and the polymer is adsorbed by stirring using a disper or the like. At this time, it is preferable to appropriately add pure water to impart fluidity.
  • the carbon material-containing aqueous solution is dried by keeping it in a thermostat. At this time, the temperature is preferably 80 ° C. or less. Treatment at a high temperature at which water boils, such as around 100 ° C., is not preferable because the uniformity of the adsorbed polymer may be reduced.
  • a step of further discharging the water by holding it at high temperature or under vacuum may be added.
  • high temperatures at which the polymer decomposes are not preferable.
  • the obtained negative electrode material is preferably crushed. Crushing is not particularly limited as long as it is a method of a general lithium ion secondary battery graphite material. As another method, a method of adding a polymer may be used when preparing the negative electrode mixture slurry. Although it is necessary to ensure the consistency with the manufacturing process, the subsequent adsorption has an advantage that the manufacturing cost can be reduced as compared with the case of the prior adsorption.
  • the method for producing the negative electrode 12 is not particularly limited.
  • the negative electrode active material, a thickener, a water-soluble binder, and in the case of post adsorption, the polymer is put in a solvent, a ball mill, a planetary mixer, etc.
  • the mixture is well kneaded and dispersed using a general mixing and dispersing method of the above to prepare a negative electrode mixture slurry.
  • this negative electrode mixture slurry is applied onto a current collector made of metal foil such as copper using a coating machine, vacuum dried at an appropriate temperature of, for example, around 100 ° C., and compressed using a press machine. After molding, it can be cut or punched into a desired size to produce the intended negative electrode 12.
  • the solvent for preparing the negative electrode mixture slurry is not particularly limited, and examples thereof include pure water, N-methyl-2-pyrrolidone (NMP), ethylene glycol, toluene, xylene and the like.
  • a non-fluorinated organic polymer such as acrylonitrile-butadiene rubber (NBR) or styrene-butadiene rubber (SBR) may be added to the negative electrode mixture.
  • NBR acrylonitrile-butadiene rubber
  • SBR styrene-butadiene rubber
  • a water-soluble polysaccharide in combination as a thickener.
  • water-soluble polysaccharides include methylcellulose, ethylcellulose, acetylcellulose, hydroxyethylcellulose, carboxymethylcellulose, starch, carrageenan, pullulan, guar gum, xanthan gum (xanthan gum), hydroxypropyl cellulose, hydroxypropyl methylcellulose and the like. Of these, some may be salted. Among these, sodium salt of carboxymethylcellulose is particularly preferable. These compounds may be used alone or in combination of two or more.
  • a copper foil having a thickness of 10 to 100 ⁇ m, a perforated copper foil having a thickness of 10 to 100 ⁇ m and a pore diameter of 0.1 to 10 mm, an expanded metal, a foam metal plate or the like is used.
  • materials such as stainless steel, titanium or nickel are also applicable.
  • any current collector can be used without being limited to the material, shape, manufacturing method and the like.
  • a negative electrode slurry obtained by mixing a negative electrode active material, a binder, and an organic solvent is attached to a current collector by a doctor blade method, a dipping method, a spray method or the like, and then the organic solvent is dried and pressure-formed by a roll press
  • the negative electrode can be manufactured.
  • the multilayer mixture layer can be formed on the current collector by performing the process from application to drying a plurality of times.
  • a material forming an alloy with lithium or a material forming an intermetallic compound may be mixed as an active material different from the above-mentioned graphite, non-graphite carbon and the like.
  • metals such as aluminum, silicon, tin and their alloys, lithium-containing transition metal nitride Li (3-x) M x N, lower oxides of silicon Li x SiO y (0 ⁇ x, 0 ⁇ y ⁇ 2) and lower oxides of tin, Li x SnO y (0 ⁇ x, 0 ⁇ y ⁇ 2).
  • You may select as a material which materials other than said material mix.
  • the positive electrode 10 includes a positive electrode active material, a conductive agent, a binder, and a current collector.
  • a positive electrode active material LiCoO 2 , LiNiO 2 , and LiMn 2 O 4 are representative examples.
  • LiMnO 3 LiMn 2 O 3 , LiMnO 2 , Li 4 Mn 5 O 12 , and LiMn 2-x MxO 2
  • LiFeO 2 , Fe 2 (SO 4 ) 3 LiCo 1 -x M x O 2 (where little is selected from the group consisting of
  • the particle size of the positive electrode active material is usually defined to be equal to or less than the thickness of the mixture layer formed from the positive electrode active material, the conductive agent, and the binder.
  • the powder of the positive electrode active material contains coarse particles having a size equal to or larger than the mixture layer thickness, the coarse particles are removed in advance by sieve classification, air flow classification, etc. to produce particles of the mixed layer thickness or less. preferable.
  • the positive electrode active material is generally oxide-based and has high electrical resistance
  • a conductive agent made of carbon powder is used to compensate for the electrical conductivity. Since both the positive electrode active material and the conductive agent are usually powders, the powders can be mixed with a binder to bond the powders together and simultaneously adhere to the current collector.
  • an aluminum foil having a thickness of 10 to 100 ⁇ m, a perforated aluminum foil having a thickness of 10 to 100 ⁇ m and a hole diameter of 0.1 to 10 mm, an expanded metal, a foam metal plate or the like is used.
  • materials such as stainless steel and titanium are also applicable.
  • any current collector can be used without being limited to the material, shape, manufacturing method and the like.
  • a positive electrode slurry obtained by mixing a positive electrode active material, a conductive agent, a binder, and an organic solvent is attached to a current collector by a doctor blade method, dipping method, spray method or the like, then the organic solvent is dried and added by a roll press.
  • the positive electrode 10 can be manufactured by pressure molding. Moreover, it is also possible to laminate a plurality of mixture layers on the current collector by performing application to drying a plurality of times.
  • the separator 11 is inserted between the positive electrode 10 and the negative electrode 12 manufactured by the above method, and a short circuit of the positive electrode 10 and the negative electrode 12 is prevented.
  • the separator 11 it is possible to use a polyolefin-based polymer sheet made of polyethylene, polypropylene or the like, or a two-layer structure in which a polyolefin-based polymer and a fluorine-based polymer sheet represented by polyethylene tetrafluoride are welded. It is.
  • a mixture of ceramics and a binder may be formed in a thin layer on the surface of the separator 11 so that the separator 11 does not shrink when the battery temperature rises. Since these separators 11 need to transmit lithium ions at the time of charge and discharge of the battery, they can generally be used in lithium ion secondary batteries if the pore size is 0.01 to 10 ⁇ m and the porosity is 20 to 90%. Is
  • Lithium hexafluorophosphate LiPF 6
  • LiPF 6 Lithium hexafluorophosphate
  • a solvent prepared by mixing ethylene carbonate with dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate or the like as a representative example of an electrolytic solution usable in one embodiment of the present invention
  • lithium borofluoride LiBF 4
  • the present invention is not limited to the type of solvent and electrolyte, and the mixing ratio of solvents, and other electrolytic solutions can also be used.
  • nonaqueous solvents examples include propylene carbonate, ethylene carbonate (EC), butylene carbonate, vinylene carbonate, ⁇ -butyrolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate.
  • 1,2-Dimethoxyethane 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, methyl propionate, ethyl propionate, phosphoric acid triester, trimethoxymethane, dioxolane, diethyl ether , Sulfolane, 3-methyl-2-oxazolidinone, tetrahydrofuran, 1,2-diethoxyethane, chloroethylene carbonate, or non-water such as chloropropylene carbonate There is a medium. Other solvents may be used as long as they do not decompose on the positive electrode 10 or the negative electrode 12 incorporated in the battery of the present invention.
  • examples of the electrolyte LiPF 6, LiBF 4, LiClO 4, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, or imide salts such as lithium represented by lithium trifluoromethane sulfonimide, multi
  • lithium salt LiPF 6, LiBF 4, LiClO 4, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, or imide salts such as lithium represented by lithium trifluoromethane sulfonimide, multi
  • a non-aqueous electrolytic solution prepared by dissolving these salts in the above-mentioned solvent can be used as a battery electrolytic solution.
  • An electrolyte other than this may be used as long as it does not decompose on the positive electrode 10 and the negative electrode 12 of the battery according to the present embodiment.
  • an ion conductive polymer such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyhexafluoropropylene, polyethylene oxide can be used as the electrolyte.
  • an ion conductive polymer such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyhexafluoropropylene, polyethylene oxide.
  • ionic liquids can be used.
  • EMI-BF4 1-ethyl-3-methylimidazolium tetrafluoroborate
  • LiTFSI lithium salt LiN (SO 2 CF 3 ) 2
  • triglyme and tetraglyme triglyme and tetraglyme
  • cyclic quaternary ammonium type cation N-methyl
  • a combination which does not decompose at the positive electrode 10 and the negative electrode 12 is selected from -N-propylpyrolidinium) and an imide type anion (bis (fluorosulfonyl) imide). It can be used for batteries.
  • the lithium ion secondary battery according to an embodiment of the present invention can be manufactured, for example, by arranging the negative electrode and the positive electrode as described above with the separator interposed therebetween and injecting the electrolyte.
  • the structure of the lithium ion secondary battery according to one embodiment of the present invention is not particularly limited, but usually, the positive electrode and the negative electrode and the separator separating them are wound to form a wound electrode group, or the positive electrode, the negative electrode and The separators can be stacked to form a stacked electrode group.
  • combination procedure of a negative electrode active material is shown.
  • coal-based coal tar was heat-treated at 400 ° C using an autoclave to obtain raw coke.
  • the raw coke was pulverized and calcined at 2800 ° C. in an inert atmosphere to obtain a carbon material having a carbon interlayer distance (d 002 ) of 0.335 nm.
  • the carbon material was crushed using an impact crusher with a classifier, and coarse particles were removed with a 300-mesh sieve to obtain carbon particles.
  • the average particle diameter at that time was 16.6 ⁇ m and the specific surface area was 5.8 m 2 / g.
  • the polymer was adsorbed to the graphite.
  • Polyvinyl sulfonate Na was used as the polymer to be adsorbed.
  • Sodium polyvinyl sulfonate was added to pure water so that the concentration of the aqueous solution would be 1.0% by mass, and the solution was stirred for 8 h with a wave rotor to prepare a solution.
  • the obtained slurry was held at 80 ° C. for 3 h for drying, and then 100 ° C. vacuum drying was performed for 4 h.
  • the obtained massive graphite was crushed with a mixer, and classified using a sieve with an aperture of 50 ⁇ m, and this was used as a negative electrode active material for a lithium ion secondary battery.
  • the average particle diameter at that time was 17.8 ⁇ m, and the specific surface area was 3.2 m 2 / g.
  • combination procedure of a positive electrode active material is shown.
  • Nickel oxide, manganese oxide and cobalt oxide were used as raw materials, weighed so that the atomic ratio of Ni: Mn: Co was 1: 1: 1, and pulverized and mixed by a wet crusher.
  • the pulverized and mixed powder to which polyvinyl alcohol (PVA) was added as a binder was granulated with a spray dryer.
  • the obtained granulated powder was placed in a high purity alumina container, and calcined for 12 hours at 600 ° C. in order to evaporate PVA, and after air cooling, it was crushed.
  • PVA polyvinyl alcohol
  • lithium hydroxide monohydrate was added to the crushed powder so that the atomic ratio of Li: transition metal (Ni, Mn, Co) would be 1: 1: 1, and thoroughly mixed.
  • the mixed powder was placed in a high purity alumina container and subjected to main firing at 900 ° C. for 6 hours.
  • the obtained positive electrode active material was crushed and classified in a ball mill. The average particle size of this positive electrode active material was 6 ⁇ m.
  • the spacing d 002 of the carbon 002 plane in the carbon material of the present example was measured using a Rigaku X-ray diffractometer RU 200 B. Cu was used for the X-ray source, and the diffraction accuracy was corrected using Si. By profile fitting the peak obtained by the measurement, it can be calculated using Bragg's equation.
  • the particle sizes (50% D) of the materials in the examples were examined using a laser diffraction / scattering particle size distribution analyzer LA-920 manufactured by Horiba, Ltd.
  • a light source 1 mW of He—Ne laser was used, and a dispersion medium of carbon particles was prepared by adding two drops of surfactant to ion-exchanged water. Ultrasonication was performed in advance for 5 minutes or more, and ultrasonication was performed during the measurement to prevent aggregation.
  • the cumulative 50% particle size (50% D) of the measurement results was taken as the average particle size.
  • the specific surface area of the carbon material which is the negative electrode active material of the lithium ion secondary battery in the example is as follows: After vacuum drying the carbon material at 120 ° C. for 3 hours, using BELSORP-mini manufactured by Nippon Bell Co., Ltd., nitrogen adsorption at 77 K The adsorption isotherm measured at an equilibration time of 300 seconds using was analyzed by BET method.
  • the volume resistivity in this example was measured using Mitsubishi Chemical Lorester GP, MCP-T610.
  • the powder resistance measured the pressure to 20 kN every 1 kN.
  • a lithium ion secondary battery was created.
  • a positive electrode was prepared.
  • a solution prepared by dissolving 7.0 parts by weight of powdered carbon and 2.0 parts by weight of acetylene black as a conductive material in 85.0 parts by weight of a positive electrode active material and 6.0 parts by weight of PVDF in NMP as a binder in advance.
  • they were further mixed by a planetary mixer to form a positive electrode mixture slurry.
  • the slurry was uniformly and uniformly coated on both sides of a 20 ⁇ m thick aluminum foil by a coating machine, and then compression molded by a roll press so that the electrode density was 2.55 g / cc, to obtain a positive electrode.
  • the negative electrode was produced. 97.0 parts by weight of the graphite as a negative electrode active material, equivalent to 1.5 parts by weight of solid content of a 1% aqueous solution of CMC (carbomethylcellulose), and equivalent to 1.5 parts by weight of solid content of a 40% aqueous solution of SBR
  • the mixture was further mixed by a planetary mixer to prepare a negative electrode mixture slurry.
  • the slurry was applied uniformly and evenly on both sides of a current collector made of rolled copper foil with a thickness of 10 ⁇ m by a coating machine, and then compression molded by a roll press to obtain a negative electrode.
  • the positive electrode and the negative electrode were cut into desired sizes, and the current collecting tabs were ultrasonically welded to the uncoated portions.
  • the current collection tab used the lead piece of aluminum for positive electrodes, and used the lead piece of nickel for negative electrodes. Thereafter, this wound body obtained by winding a 30 ⁇ m thick separator while sandwiching a porous polyethylene film between the positive electrode and the negative electrode is inserted into the battery can, and the negative electrode tab is connected to the can bottom of the battery can by resistance welding.
  • the positive electrode lid was connected by ultrasonic welding.
  • An electrolyte prepared by dissolving 1 mol / liter of LiPF 6 in a mixed solvent of 1: 1, 1: 1 by volume ratio of EC, DMC, and DEC is injected, and then the positive electrode lid is crimped on a battery can and sealed. , Obtained a lithium ion secondary battery.
  • the direct current resistance (DCR) of the battery was measured to determine the power density of the battery.
  • the manufactured battery was charged to 4.1 V with a current corresponding to 0.3 C at around normal temperature (25 ° C.), and then constant-voltage charging was performed at 4.1 V until the current was 0.03 C.
  • constant current discharge was performed to 2.7 V with a constant current of 0.3 C equivalent.
  • Four cycles are performed to initialize, and the capacity density mAh / g per battery weight is determined from the discharge capacity at the fourth cycle.
  • constant current charge is performed to 3.6 V at 0.3 C, and then currents 4CA, 8CA, 12CA, It was discharged for 10 seconds at a current value of 16 CA. The voltage value at this time was determined, and the output density was determined from the limiting current when this was extrapolated to 2.5 V.
  • Table 1 The results are shown in Table 1.
  • the cells were then subjected to a crush test as a reliability test.
  • the battery was subjected to a crushing test by performing constant voltage and constant current charging with a charging voltage of 4.1 V, a charging time of 2 hours, and a limiting current of 800 mA.
  • this round bar was pressed against the center of the cell from the direction perpendicular to the direction in which the outer dimensions of the cell were longest, and the cell was crushed to half its thickness .
  • the results were classified as no change, valve operation only, valve operation + smoke generation, valve operation + smoke generation + ignition.
  • valve operation is the state where the safety valve is open
  • valve operation + smoke is the state where the safety valve is open and the gas is spouted simultaneously
  • valve operation + smoke + ignition is the state that the gas spouts from the battery and it is ignited.
  • Example 2 The same procedure as in Example 1 was carried out except that the aqueous solution concentration of polyvinyl sulfonic acid Na was made 0.5 mass%, and the addition amount at the time of mixing with graphite was made 200 g.
  • Example 2 The same procedure as in Example 1 was carried out except that the aqueous solution concentration of polyvinyl sulfonate Na was changed to 2.0% by mass, and the addition amount at the time of mixing with graphite was changed to 50 g.
  • Example 2 The same procedure as in Example 1 was carried out except that the amount of polymer added to graphite was 200 g in the case of mixing sodium polyvinyl sulfonate and graphite so that the polymer solid content ratio was 2% by mass.
  • the amount of polymer added to graphite was 200 g in the case of mixing sodium polyvinyl sulfonate and graphite so that the polymer solid content ratio was 2% by mass.
  • the treatment to carbon was performed in the same manner as in Example 1 except that WO 3 was added to 100 nm by CVD.
  • Example 1 It carried out like Example 1 except not having performed processing to carbon.
  • Example 2 The same procedure as in Example 1 was carried out except that the aqueous solution concentration of sodium poly (vinyl sulfonate) was 10% by mass, and the addition amount at the time of mixing with graphite was 10 g.
  • Example 3 The same procedure as in Example 1 was carried out except that the aqueous solution concentration of sodium poly (vinyl sulfonate) was set to 4.0 mass%, and the amount added when mixing with graphite was set to 50 g.
  • Example 4 The same procedure as in Example 1 was carried out except that the aqueous solution concentration of sodium poly (vinyl sulfonate) was set to 5.0% by mass, and the addition amount at the time of mixing with graphite was set to 20 g.
  • Example 1-6 and Comparative Example 1-4 in Table 1 when the volume resistivity at a density of 2.0 g / cc is less than 0.32 ⁇ ⁇ cm, 4.1 V and 4.3 V in the crushing test. Smoke and ignition were observed in the case, but when the volume resistivity at a density of 2.0 g / cc was 0.32 ⁇ ⁇ cm or more, no ignition was observed at 4.1 V and 4.3 V in the crushing test It is clear from this that the reliability is improved.
  • Example 1-6 and Comparative Example 5 are compared, even if the volume resistivity at a density of 2.0 g / cc is 0.32 ⁇ ⁇ cm or more, the volume resistivity at the time of changing from low density to high density When the decrease of is large, the DCR rises sharply and the power density decreases.
  • the lithium ion secondary battery provided by the present invention is a lithium ion secondary battery in which the reliability of the battery after cycle deterioration is improved while minimizing the increase in battery resistance as compared with the prior art. That was confirmed.

Abstract

A negative electrode active material for a lithium ion secondary cell in which lithium ions are stored and released, characterized in that: the negative electrode active material has a core composed of carbon, has a volume resistivity of 0.32 Ω·cm or greater at a density of 2.0 g/cc, and satisfies the formula (1) r2≧0.13×r1 (where r2 is volume resistivity at a density of 2.0 g/cc, and r1 is volume resistivity at a density of 1.2 g/cc); and the carbon has a surface separation of 0.334-0.338 nm for the carbon (002) plane, as determined by X-ray diffractometer measurements. A lithium ion secondary cell having increased reliability can be provided by using this negative electrode active material. In particular, a large electric current during cycle degradation can be reduced.

Description

リチウムイオン二次電池用負極活物質及びそれらを用いたリチウムイオン二次電池Negative electrode active material for lithium ion secondary battery and lithium ion secondary battery using them
　本発明は、リチウムイオン二次電池用負極活物質及びそれらを用いたリチウムイオン二次電池に関する。 The present invention relates to a negative electrode active material for a lithium ion secondary battery and a lithium ion secondary battery using them.
　近年、リチウムイオン二次電池に対する開発が盛んに進められている。１９８０年代，１９９０年代の携帯電話やノートＰＣの発達に伴い、それらの電源用として二次電池は高性能化されている。二次電池としては鉛蓄電池やニッカド電池より、高エネルギー密度を持つリチウムイオン二次電池が主に用いられている。 In recent years, development for lithium ion secondary batteries has been actively promoted. With the development of mobile phones and notebook PCs in the 1980's and 1990's, the performance of secondary batteries has been improved as their power source. As a secondary battery, a lithium ion secondary battery having a high energy density is mainly used rather than a lead storage battery or a Ni-Cd battery.
　負極活物質としてリチウムイオンの吸蔵・放出が可能な炭素材料を用いた場合、充電時に、炭素材料の層間にリチウムイオンが吸蔵されるため、負極上に金属リチウムが析出することがなく、デンドライトによる内部短絡の問題を回避することができる。しかしながら、負極材料として炭素材料を用いた電池においても、電池内で正極と負極とが接触し、内部短絡が発生することがある。内部短絡が発生すると、正極と負極とが接触した部分に大電流が集中するとともに発熱が起こり、電池の温度が急激に上昇して発火に至る可能性がある。 When a carbon material capable of absorbing and desorbing lithium ions is used as the negative electrode active material, lithium ions are absorbed between the layers of the carbon material during charging, and therefore metallic lithium does not precipitate on the negative electrode, and dendrites The problem of internal short circuit can be avoided. However, even in a battery using a carbon material as the negative electrode material, the positive electrode and the negative electrode may be in contact in the battery, and an internal short circuit may occur. When an internal short circuit occurs, a large current is concentrated at a portion where the positive electrode and the negative electrode are in contact with each other and heat is generated, and the temperature of the battery may be rapidly increased to cause ignition.
　また、リチウムイオン二次電池の電解液には、主に非水溶媒が用いられている。従って、過充電，加熱，短絡などが生じても発熱暴走状態となったりせず、さらに、電池が破裂発火しないよう信頼性の確保が重要である。 In addition, non-aqueous solvents are mainly used in the electrolyte solution of lithium ion secondary batteries. Therefore, even if overcharging, heating, or a short circuit occurs, the heat generation runaway state does not occur, and it is important to ensure the reliability so that the battery does not burst and ignite.
　信頼性を高めるための技術として、特開２００４－３９５５８号公報（特許文献１）では、正負極に、１８０℃における体積抵抗率が－２０℃以上～６０℃における体積抵抗率に比べて２.５倍以上である導電材を設けることが開示されている。その結果、短絡電流による急激な温度上昇を抑制することができる。 As a technique for enhancing the reliability, according to JP-A-2004-39558 (Patent Document 1), the positive and negative electrodes have a volume resistivity at 180 ° C. which is greater than that at −20 ° C. to 60 ° C. It is disclosed to provide a conductive material that is five times or more. As a result, it is possible to suppress a rapid temperature rise due to the short circuit current.
　さらに、特開２０１１－７６８２２号公報（特許文献２）には、負極活物質層の体積抵抗率を上昇させることが開示されている。 Further, JP 2011-76822 A (Patent Document 2) discloses that the volume resistivity of the negative electrode active material layer is increased.
特開２００４－３９５５８号公報JP 2004-39558 A 特開２０１１－７６８２２号公報JP, 2011-76822, A
　特許文献１のように、高温にならないと短絡電流が抑えられないシャットダウン機構には、常温での発熱を穏やかにする効果がない。従って、１００～２００℃以下で電流を流れにくくすることができても、急激な発熱では、正極や負極や電解液がそれまでに自己発熱する温度に達してしまうと、継続的に発熱が起こり、熱暴走してしまうおそれがある。 As in Patent Document 1, the shutdown mechanism in which the short circuit current can not be suppressed unless the temperature is high does not have an effect of moderating heat generation at normal temperature. Therefore, even if current can be made difficult to flow at 100 to 200 ° C. or less, sudden heat generation causes continuous heat generation if the temperature of the positive electrode, negative electrode or electrolyte reaches self-heating by then. There is a risk of thermal runaway.
　特許文献２のように、体積抵抗率を単純に増大させる場合、サイクル劣化後の信頼性向上への寄与が小さい。また、電池の抵抗を増大させてしまうおそれがある。 When the volume resistivity is simply increased as in Patent Document 2, the contribution to the improvement of reliability after cycle deterioration is small. In addition, the battery resistance may be increased.
　従って本発明の目的は、電池の抵抗の上昇を抑制しつつ、リチウムイオン二次電池の信頼性を向上させることにある。 Therefore, an object of the present invention is to improve the reliability of a lithium ion secondary battery while suppressing an increase in battery resistance.
　上記課題を解決するための本発明の特徴は以下の通りである。リチウムイオンを吸蔵・放出するリチウムイオン二次電池用負極活物質であって、前記負極活物質は、炭素よりなる核材を有し、密度２．０ｇ／ｃｃにおける体積抵抗率が、０．３２Ω・ｃｍ以上で、かつ式（１）を満たし、前記炭素は、Ｘ線回折装置測定により求められる炭素００２面の面間隔が０．３３４ｎｍ以上０．３３８ｎｍ以下であることを特徴とするリチウムイオン二次電池負極活物質。
　式（１）： ｒ2≧０．１３× ｒ1
式（１）において、ｒ2は、密度２．０ｇ／ｃｃにおける体積抵抗率、ｒ1は、密度１．２ｇ／ｃｃにおける体積抵抗率を表す。 The features of the present invention for solving the above problems are as follows. A negative electrode active material for a lithium ion secondary battery that absorbs and releases lithium ions, wherein the negative electrode active material has a core material made of carbon, and has a volume resistivity of 0.32 Ω at a density of 2.0 g / cc. · A lithium ion diode characterized in that it is cm or more and satisfies the formula (1), and the carbon has a spacing of 0.334 nm to 0.338 nm between the carbon 002 planes determined by X-ray diffractometer measurement. Next battery negative electrode active material.
Formula (1): r 2 0.10.13 × r 1
In the formula (1), r 2 is the volume resistivity in the density of 2.0 g / cc, r 1 represents the volume resistivity at a density 1.2 g / cc.
　本発明によると、電池の抵抗の上昇を抑制しつつ、リチウムイオン二次電池の信頼性を向上させたリチウムイオン二次電池用負極活物質を提供することができる。特に、サイクル劣化後の電池での効果が大きい。上記した以外の課題、構成及び効果は以下の実施形態の説明により明らかにされる。 ADVANTAGE OF THE INVENTION According to this invention, the negative electrode active material for lithium ion secondary batteries which improved the reliability of the lithium ion secondary battery can be provided, suppressing the raise of the resistance of a battery. In particular, the effect of the battery after cycle deterioration is large. Problems, configurations, and effects other than those described above will be apparent from the description of the embodiments below.
本発明の一実施形態に係る電池の内部構造を模式的に表す図である。It is a figure showing typically the internal structure of the battery concerning one embodiment of the present invention.
　以下、図面等を用いて、本発明の実施形態について説明する。以下の説明は本発明の内容の具体例を示すものであり、本発明がこれらの説明に限定されるものではなく、本明細書に開示される技術的思想の範囲内において当業者による様々な変更および修正が可能である。また、本発明を説明するための全図において、同一の機能を有するものは、同一の符号を付け、その繰り返しの説明は省略する場合がある。 Hereinafter, embodiments of the present invention will be described using the drawings and the like. The following description shows specific examples of the content of the present invention, and the present invention is not limited to these descriptions, and various modifications by those skilled in the art can be made within the scope of the technical idea disclosed herein. Changes and modifications are possible. Moreover, in all the drawings for explaining the present invention, what has the same function may attach the same numerals, and may omit explanation of the repetition.
　本明細書において「工程」との語は、独立した工程だけではなく、他の工程と明確に区別できない場合であってもその工程の所期の作用が達成されれば、本用語に含まれる。また、本明細書において「～」を用いて示された数値範囲は、「～」の前後に記載される数値をそれぞれ最小値及び最大値として含む範囲を示す。本明細書で引用した全ての刊行物、特許及び特許出願をそのまま参考として本明細書に取り入れるものとする。 In the present specification, the term "process" is included in the term if the intended function of the process is achieved, even if it can not be clearly distinguished from other processes, not only the independent process. . Further, in the present specification, a numerical range indicated using “to” indicates a range including numerical values described before and after “to” as the minimum value and the maximum value, respectively. All publications, patents and patent applications cited herein are incorporated herein by reference in their entirety.
　図１は、本発明の一実施形態に係る電池の内部構造を模式的に表す図である。図１に示す本発明の一実施形態に係る電池１は、正極１０、セパレータ１１、負極１２、電池缶１３、正極集電タブ１４、負極集電タブ１５、内蓋１６、内圧開放弁１７、ガスケット１８、正温度係数（Ｐｏｓｉｔｉｖｅ　ｔｅｍｐｅｒａｔｕｒｅ　ｃｏｅｆｆｉｃｉｅｎｔ；ＰＴＣ）抵抗素子１９、及び電池蓋２０、軸心２１から構成される。電池蓋２０は、内蓋１６、内圧開放弁１７、ガスケット１８、及び抵抗素子１９からなる一体化部品である。また、軸心２１には、正極１０、セパレータ１１及び負極１２が捲回されている。 FIG. 1 is a view schematically showing an internal structure of a battery according to an embodiment of the present invention. A battery 1 according to an embodiment of the present invention shown in FIG. 1 includes a positive electrode 10, a separator 11, a negative electrode 12, a battery can 13, a positive current collecting tab 14, a negative current collecting tab 15, an inner lid 16, an internal pressure release valve 17, A gasket 18, a positive temperature coefficient (PTC) resistance element 19, a battery cover 20, and an axial center 21 are provided. The battery lid 20 is an integrated component including the inner lid 16, the internal pressure release valve 17, the gasket 18, and the resistance element 19. Further, the positive electrode 10, the separator 11 and the negative electrode 12 are wound around the axial center 21.
　セパレータ１１を正極１０及び負極１２の間に挿入し、軸心２１に捲回した電極群を作製する。軸心２１は、正極１０、セパレータ１１及び負極１２を担持できるものであれば、公知の任意のものを用いることができる。電極群は、図１に示した円筒形状の他に、短冊状電極を積層したもの、又は正極１０と負極１２を扁平状等の任意の形状に捲回したもの等、種々の形状にすることができる。電池缶１３の形状は、電極群の形状に合わせ、円筒形、偏平長円形状、扁平楕円形状、角形等の形状を選択してもよい。 The separator 11 is inserted between the positive electrode 10 and the negative electrode 12, and an electrode group wound around the axial center 21 is produced. As the shaft 21, any known one can be used as long as it can support the positive electrode 10, the separator 11 and the negative electrode 12. In addition to the cylindrical shape shown in FIG. 1, the electrode group may be formed into various shapes, such as one obtained by laminating strip electrodes, or one obtained by winding the positive electrode 10 and the negative electrode 12 into an arbitrary shape such as flat. Can. The shape of the battery can 13 may be a cylindrical shape, a flat oval shape, a flat oval shape, a square shape, or the like in accordance with the shape of the electrode group.
　電池缶１３の材質は、アルミニウム、ステンレス鋼、ニッケルメッキ鋼製等、非水電解質に対し耐食性のある材料から選択される。また、電池缶１３を正極１０又は負極１２に電気的に接続する場合は、非水電解質と接触している部分において、電池缶１３の腐食やリチウムイオンとの合金化による材料の変質が起こらないように、電池容器１３の材料の選定を行う。 The material of the battery can 13 is selected from materials having corrosion resistance to the non-aqueous electrolyte, such as aluminum, stainless steel, nickel plated steel, and the like. Moreover, when the battery can 13 is electrically connected to the positive electrode 10 or the negative electrode 12, the material of the battery can 13 does not deteriorate due to corrosion or alloying with lithium ions in a portion in contact with the non-aqueous electrolyte. Thus, the material of the battery case 13 is selected.
　電池缶１３に電極群を収納し、電池缶１３の内壁に負極集電タブ１５を接続し、電池蓋２０の底面に正極集電タブ１４を接続する。電解液は、電池の密閉の前に電池缶１３の内部に注入する。電解液の注入方法は、電池蓋２０を解放した状態にて電極群に直接添加する方法、又は電池蓋２０に設置した注入口から添加する方法がある。 The electrode group is housed in the battery can 13, the negative electrode current collecting tab 15 is connected to the inner wall of the battery can 13, and the positive electrode current collecting tab 14 is connected to the bottom surface of the battery cover 20. The electrolyte is injected into the inside of the battery can 13 before sealing the battery. As a method of injecting the electrolytic solution, there is a method of adding directly to the electrode group in a state in which the battery cover 20 is released, or a method of adding from an injection port provided on the battery cover 20.
　その後、電池蓋２０を電池缶１３に密着させ、電池全体を密閉する。電解液の注入口がある場合は、それも密封する。電池を密閉する方法には、溶接、かしめ等公知の技術がある。 Thereafter, the battery cover 20 is brought into close contact with the battery can 13 to seal the entire battery. If there is an electrolyte inlet, seal it as well. As a method of sealing the battery, there are known techniques such as welding and caulking.
　本発明の一実施形態に係るリチウムイオン二次電池は、例えば、下記のような負極と正極とをセパレータを介して対向して配置し、電解質を注入することによって製造することができる。本発明の一実施形態に係るリチウムイオン二次電池の構造は特に限定されないが、通常、正極及び負極とそれらを隔てるセパレータとを捲回して捲回式電極群にするか、又は正極、負極及びセパレータを積層させて積層型の電極群とすることができる。 The lithium ion secondary battery according to one embodiment of the present invention can be manufactured, for example, by arranging the following negative electrode and positive electrode as opposed to each other with the separator interposed therebetween, and injecting an electrolyte. The structure of the lithium ion secondary battery according to one embodiment of the present invention is not particularly limited, but usually, the positive electrode and the negative electrode and the separator separating them are wound to form a wound electrode group, or the positive electrode, the negative electrode and The separators can be stacked to form a stacked electrode group.
　図１に示す電池の構成は、本発明の一実施形態に係るリチウムイオン二次電池用負極活物質を適用可能なリチウムイオン二次電池の内部構造のあくまでも一例であり、本発明の一実施形態に係る負極が適用可能な電池は図１に記載のものに制限されるものでない。 The configuration of the battery shown in FIG. 1 is merely an example of the internal structure of a lithium ion secondary battery to which the negative electrode active material for a lithium ion secondary battery according to an embodiment of the present invention can be applied, and an embodiment of the present invention The battery to which the negative electrode according to the present invention is applicable is not limited to the one described in FIG.
＜負極＞
　前記の問題に鑑み、発明者らが鋭意検討を行った結果、サイクル劣化後のリチウムイオン二次電池の信頼性には、高密度時の体積抵抗率が大きい負極活物質を用いる事が重要である事がわかった。負極活物質として黒鉛を用いた場合、サイクル劣化後の負極は、負極中の黒鉛が膨張収縮により移動することで、負極内に黒鉛粒子の分布が生まれ、黒鉛が疎な部分と密な部分が存在する。そして、内部短絡が発生した際に黒鉛が密な部分で大電流が流れると推測される。この黒鉛が密な負極部分で流れる常温での電流を抑制することが、内部短絡が発生した際の発火を防ぐ点において、重要であることを見出した。黒鉛が高密度になった箇所は、低密度の箇所に比べて電子伝導性が高く、大電流が流れてしまうため、高密度時の体積抵抗率の大きな黒鉛を用いることが重要である。 <Negative electrode>
In view of the above problems, as a result of intensive investigations by the inventors, it is important to use a negative electrode active material having high volume resistivity at high density for reliability of the lithium ion secondary battery after cycle deterioration. I understand that there is a thing. When graphite is used as the negative electrode active material, in the negative electrode after cycle deterioration, the graphite in the negative electrode moves due to expansion and contraction to create a distribution of graphite particles in the negative electrode, and the dense and sparse portions of the graphite Exists. Then, when an internal short circuit occurs, it is presumed that a large current flows in a portion where the graphite is dense. It has been found that suppressing the current at ordinary temperature at which the graphite flows in the dense negative electrode portion is important in terms of preventing ignition when an internal short circuit occurs. It is important to use graphite having a high volume resistivity at high density, since the high density of the graphite has high electron conductivity and a large current flows as compared with the low density part.
　一方で、サイクル劣化後の黒鉛が高密度な状態に比べて、黒鉛が低密度な状態での体積抵抗率は大きくないことが好ましい。低密度での体積抵抗率が大きい場合、電子伝導性が低下し、電池の抵抗が大きくなってしまうからである。また、サイクル劣化後の電流は高密度領域で流れるため、リチウムイオン二次電池の信頼性の向上への効果も小さい。 On the other hand, it is preferable that the volume resistivity in the state of low density of graphite is not large compared with the state of high density of graphite after cycle deterioration. When the volume resistivity at low density is large, the electron conductivity is lowered and the resistance of the battery is increased. In addition, since the current after cycle deterioration flows in the high density region, the effect of improving the reliability of the lithium ion secondary battery is also small.
　すなわち、低密度から高密度に変化した際の体積抵抗率の減少量が小さい負極活物質を用いる事で、初期の抵抗が小さくサイクル劣化後の電池の信頼性向上を両立出来ることを見出した。 That is, it has been found that by using a negative electrode active material with a small decrease in volume resistivity when changing from low density to high density, it is possible to simultaneously improve the reliability of the battery after cycle deterioration with a small initial resistance.
　本発明の負極活物質は、ＸＲＤ測定により求められる炭素００２面の面間隔が０．３３４ｎｍ～０．３３８ｎｍの炭素材料であって、密度２．０ｇ／ｃｃにおける体積抵抗率が、０．３２Ω・cm以上でかつ以下式（１）を満たす事を特徴としたリチウムイオン二次電池負極用炭素粒子である。
　式（１）　　　　　　ｒ2≧０．１３× ｒ1
　　　　　　　ｒ1は、密度１．２ｇ／ｃｃの体積抵抗率
　　　　　　　ｒ2は、密度２．０ｇ／ｃｃの体積抵抗率 The negative electrode active material of the present invention is a carbon material having a spacing of 0.334 nm to 0.338 nm between the carbon 002 planes determined by XRD measurement, and has a volume resistivity of 0.32 Ω · at a density of 2.0 g / cc. It is a carbon particle for lithium ion secondary battery negative electrodes characterized by not less than cm and satisfying the following formula (1).
Formula (1) r 2 0.10.13 × r 1
r 1 is volume resistivity with a density of 1.2 g / cc r 2 is volume resistivity with a density of 2.0 g / cc
　密度２．０ｇ／ｃｃにおける体積抵抗率が、０．３２Ω・ｃｍ未満の場合、サイクル劣化後のリチウムイオン二次電池の信頼性が低下するおそれがある。２．０ｇ／ｃｃの体積抵抗率は０．３３Ω・ｃｍ以上が好ましく、さらに０．３４Ω・ｃｍ以上が好ましい。 If the volume resistivity at a density of 2.0 g / cc is less than 0.32 Ω · cm, the reliability of the lithium ion secondary battery after cycle deterioration may be reduced. The volume resistivity of 2.0 g / cc is preferably 0.33 Ω · cm or more, and more preferably 0.34 Ω · cm or more.
　またｒ2＜０．１３× ｒ1の場合、電池の初期の抵抗が増大してしまうため、好ましくない。ｒ2≧０．１３× ｒ1を満たすこと好ましく、ｒ2≧０．１４× ｒ1を満たす方がさらに好ましい。 In the case of r 2 <0.13 × r 1 , the initial resistance of the battery is increased, which is not preferable. preferably satisfying r 2 ≧ 0.13 × r 1, it is further preferable to satisfy r 2 ≧ 0.14 × r 1.
　負極の体積抵抗率を増大させる手段の例として、炭素活物質表面に酸化物や窒化物等の無機物や、ポリマー等で吸着もしくは被覆する方法が挙げられる。なお、本発明の吸着は物理吸着を表す。 Examples of means for increasing the volume resistivity of the negative electrode include a method in which the surface of the carbon active material is adsorbed or coated with an inorganic substance such as an oxide or a nitride, or a polymer. In addition, adsorption of the present invention represents physical adsorption.
　吸着、被覆させる材料は、黒鉛表面になるべく均一、平滑で存在出来る事が好ましい。不均一な場合、低密度から高密度へ変化した際の体積抵抗率の減少が大きい傾向がある。 It is preferable that the material to be adsorbed and coated be present on the surface of the graphite as uniformly, as smoothly as possible. In the case of non-uniformity, the decrease in volume resistivity when changing from low density to high density tends to be large.
　また、吸着、被覆させる材料は、高密度時に変形、切断、崩壊が起こりにくい材料が好ましい。特に切断、崩壊が起こった場合、低密度から高密度へ変化した際の体積抵抗率の減少が大きい傾向がある。 Further, the material to be adsorbed and coated is preferably a material which is less likely to be deformed, cut or disintegrated at high density. In particular, when cutting or collapsing occurs, the decrease in volume resistivity when changing from low density to high density tends to be large.
　酸化物で被覆する場合、材料はリチウムイオンと合金化しない材料が好ましい。リチウムイオンと合金化する材料は、合金化することで膨張しやすく、このような材料を用いた場合サイクル特性が悪化する場合がある。 In the case of oxide coating, the material is preferably a material that is not alloyed with lithium ions. A material to be alloyed with lithium ion is easily expanded by alloying, and when such a material is used, cycle characteristics may be deteriorated.
　吸着、被覆させる材料は、窒化物や、酸化物やポリマーの中では特にポリマーが好ましい。ポリマーの場合、無機物や、酸化物に比べて比較的安価でかつ平滑に吸着させやすいためである。 The material to be adsorbed and coated is preferably a nitride, and particularly a polymer among oxides and polymers. In the case of a polymer, it is because it is relatively inexpensive and easily adsorbed smoothly as compared with inorganic substances and oxides.
　ポリマーとして具体的には、ポリビニルスルホン酸、ポリビニルスルホン酸Ｎａ、ポリスチレンスルホン酸、ポリスチレンスルホン酸Ｎａ、ポリアクリル酸，ポリアクリル酸塩，ポリアクリル酸エステル，ポリメタクリル酸，ポリメタクリル酸塩，ポリメタクリル酸エステル等が挙げられる。ポリマーの重量平均分子量は、１万～１２０万であることが望ましい。上記の重量平均分子量は、液体クロマトグラフィーにより測定した値とする。 Specifically as the polymer, polyvinylsulfonic acid, polyvinylsulfonic acid Na, polystyrenesulfonic acid, polystyrenesulfonic acid Na, polyacrylic acid, polyacrylic acid salt, polyacrylic acid ester, polymethacrylic acid, polymethacrylic acid salt, polymethacrylic acid An acid ester etc. are mentioned. The weight average molecular weight of the polymer is preferably 10,000 to 1.2 million. The above weight average molecular weight is a value measured by liquid chromatography.
　溶解性の観点から、ポリマーは、重合性官能基としてビニル基、スチレン基を有するモノマーの重合体であることが望ましい。 From the viewpoint of solubility, the polymer is preferably a polymer of a monomer having a vinyl group or a styrene group as a polymerizable functional group.
　また、極性の観点からは、ポリマーは、ビニル基よりもスチレン基のような芳香族化合物を持つモノマーの重合体であることが好ましい。極性を高くすることで、吸着均一性が向上するためである。 From the viewpoint of polarity, the polymer is preferably a polymer of a monomer having an aromatic compound such as a styrene group rather than a vinyl group. It is because adsorption uniformity improves by making polarity high.
　ポリマーは、硫黄含有官能基を有することが特に好ましい。硫黄含有官能基としては、例えば、スルホン酸基、スルホン酸塩基、スルホニル基、チオール基、スルフィド基等が挙げられる。これらの官能基は極性が高く、吸着均一性が向上するためである。硫黄含有官能基として、これらの官能基を一種単独または複数種用いても良い。吸着均一性が向上することによって、低密度から高密度へ変化した際の体積抵抗率の減少が小さくなる。 It is particularly preferred that the polymer has a sulfur containing functional group. As a sulfur containing functional group, a sulfonic acid group, a sulfonic acid group, a sulfonyl group, a thiol group, a sulfide group etc. are mentioned, for example. These functional groups have high polarity, and the adsorption uniformity is improved. One or more of these functional groups may be used as the sulfur-containing functional group. The improved adsorption uniformity reduces the decrease in volume resistivity when changing from low density to high density.
　また、ｐＨの観点では特に官能基を塩にしている物が好ましい。例えば、アルカリ金属塩であり、カウンターイオンとしてはＬｉ，Ｎａ，Ｋ，Ｃａ等を挙げることが出来る。この中では、ＬｉおよびＮａが特に好ましい。 In addition, from the viewpoint of pH, in particular, those having a functional group as a salt are preferable. For example, it is an alkali metal salt, and Li, Na, K, Ca etc. can be mentioned as a counter ion. Among these, Li and Na are particularly preferable.
　また、炭素表面を被覆する無機物としては、たとえばＣａＯ，Ｓｃ2Ｏ3，ＳｒＯ2，ＳｎＯ2，ＢａＯ，Ｌａ2Ｏ3，Ｎｄ2Ｏ3，ＷＯ3，Ａｌ2Ｏ3，ＳｉＯ2等の酸化物、またはＡｌＮ，ＧａＮ，ＳｉＮ等の窒化物、またはこれらの混合物を用いることができる。また、炭素表面を被覆する方法としてはたとえば溶液からの塗布法，蒸着法，ラングミュアブロジェット（ＬＢ）法，電解重合法，プラズマ重合法，ＣＶＤ（ｃｈｅｍｉｃａｌ　ｖａｐｏｒ　ｄｅｐｏｓｉｔｉｏｎ）法，スパッタリング法などを用いることができる。 As the inorganic substance for coating the carbon surface, eg CaO, Sc 2 O 3, SrO 2, SnO 2, BaO, La 2 O 3, Nd 2 O 3, WO 3, Al 2 O 3, oxides such as SiO 2 Or nitrides such as AlN, GaN, SiN, etc., or mixtures thereof. In addition, as a method of coating the carbon surface, for example, using a coating method from a solution, a vapor deposition method, a Langmuir Blojet (LB) method, an electrolytic polymerization method, a plasma polymerization method, a CVD (chemical vapor deposition) method, a sputtering method Can.
　本発明の一実施形態における負極１２は、上記の負極活物質、バインダ及び集電体を含む。高レート充放電が必要な場合には、導電剤を添加することもある。 The negative electrode 12 in an embodiment of the present invention includes the above-described negative electrode active material, a binder, and a current collector. When high rate charge and discharge are required, a conductive agent may be added.
　本発明の一実施形態で使用可能なポリマーが吸着した負極活物質（核材）としては、黒鉛を選択することができる。黒鉛は、黒鉛層間距離（ｄ002）が０．３３４ｎｍ以上０．３３８ｎｍ以下であることが好ましい。０．３３８ｎｍを超えると活物質の容量が小さく、電池の容量が小さくなってしまうため好ましくない。 Graphite can be selected as the negative electrode active material (nucleus material) to which the polymer usable in the embodiment of the present invention is adsorbed. The graphite preferably has a graphite interlayer distance (d 002 ) of 0.334 nm or more and 0.338 nm or less. If it exceeds 0.338 nm, the capacity of the active material will be small, and the capacity of the battery will be small.
　負極活物質としての黒鉛は、リチウムイオンを化学的に吸蔵・放出可能な天然黒鉛、人造黒鉛、メソフェ－ズ炭素、膨張黒鉛、炭素繊維、気相成長法炭素繊維、ピッチ系炭素質材料、ニードルコークス、石油コークス、及びポリアクリロニトリル系炭素繊維等を原料として製造される。なお、上記の黒鉛層間距離（ｄ002）は、ＸＲＤ（Ｘ線粉末回折法）（Ｘ－Ｒａｙ　Ｄｉｆｆｒａｃｔｉｏｎ　Ｍｅｔｈｏｄ）等を用いて測定することができる。 Graphite as the negative electrode active material is natural graphite capable of absorbing and desorbing lithium ions chemically, artificial graphite, mesophase carbon, expanded graphite, carbon fiber, vapor grown carbon fiber, pitch-based carbonaceous material, needle It is manufactured using coke, petroleum coke, polyacrylonitrile carbon fiber, etc. as a raw material. The above-mentioned graphite interlayer distance (d 002 ) can be measured using XRD (X-Ray Diffraction Method) or the like.
　負極活物質へのポリマーを吸着させる方法は以下の方法を用いることが出来る。但し、上記特徴を満たしているのであれば、その限りではない。 The following methods can be used to adsorb the polymer to the negative electrode active material. However, as long as the above-mentioned feature is satisfied, it is not the limitation.
　負極活物質の粒径は、負極活物質及びバインダから形成される負極合剤層の厚さ以下にすることが望ましい。負極活物質の粉末中に負極合剤層厚さ以上のサイズを有する粗粒がある場合、予めふるい分級や風流分級等により粗粒を除去し、負極合剤層の厚さ以下の粒子を使用することが好ましい。 The particle diameter of the negative electrode active material is desirably equal to or less than the thickness of the negative electrode mixture layer formed of the negative electrode active material and the binder. If the powder of the negative electrode active material contains coarse particles having a size greater than or equal to the layer thickness of the negative electrode mixture, the coarse particles are removed beforehand by sieve classification, air flow classification, etc., and particles smaller than the thickness of the negative electrode mixture layer are used. It is preferable to do.
　具体的な粒径としては、レーザ回折／散乱式粒度分布測定装置により求めた平均粒径が、３μｍ以上３０μｍ以下であることが好ましく、さらに３μｍ以上２５μｍ以下、特に５μｍ以上２０μｍ以下であることが好ましい平均粒径が３０μｍを超える場合、電極に凹凸ができやすくなるため、電池特性が低下する場合がある。また、３μｍ未満である場合、黒鉛がつぶれ難くなるため、密度を上げにくくなる傾向がある。なお、粒度分布は界面活性剤を含んだ精製水に試料を分散させ、レーザ回折／散乱式粒度分布測定装置で測定することができ、平均粒径は累積５０％粒径（５０％Ｄ）として算出される。 The specific particle size is preferably 3 to 30 μm, more preferably 3 to 25 μm, particularly 5 to 20 μm, as determined by a laser diffraction / scattering particle size distribution analyzer. If the preferable average particle size exceeds 30 μm, the electrode characteristics may be easily uneven, and the battery characteristics may be deteriorated. Moreover, when it is less than 3 μm, since the graphite is hardly crushed, the density tends to be difficult to increase. The particle size distribution can be measured by dispersing the sample in purified water containing a surfactant and using a laser diffraction / scattering type particle size distribution analyzer, and the average particle size is 50% cumulative (50% D). It is calculated.
　０．１ｍ2／ｇ未満の場合は、負極活物質とリチウムイオンとの反応面積が減少するため、充放電特性が悪化する場合がある。また、１０ｍ2／ｇを超える場合は、電解質との反応が起こりやすくなるため、不可逆容量が増大してしまい、寿命特性が悪化する恐れがある。 In the case of less than 0.1 m 2 / g, the reaction area of the negative electrode active material and the lithium ion is reduced, so that the charge and discharge characteristics may be deteriorated. In addition, if it exceeds 10 m 2 / g, reaction with the electrolyte is likely to occur, so the irreversible capacity may be increased, and the life characteristics may be deteriorated.
　吸着させるポリマーは、吸着均一性を高める観点から予め純水に溶かして水溶液にしておくのが好ましい。ポリマー水溶液の作製方法は、特に限定されないが、溶け残りは不均一化の原因となるため、溶け残りが無いように注意する必要がある。例えば、プロペラやウエーブロータで撹拌しながら少量ずつ添加する事で溶解することが出来る。この際、必要に応じて熱をかけても構わない。また、溶解後の水溶液の濾過を実施しても構わない。ポリマー水溶液の濃度は特に限定されないが、溶け残りの観点を考えると、０．５～２．０質量％前後である事が好ましい。濃度が薄すぎる、もしくは濃すぎる場合、均一吸着性が低下する。 The polymer to be adsorbed is preferably dissolved in pure water beforehand to be an aqueous solution from the viewpoint of enhancing the adsorption uniformity. The method for producing the polymer aqueous solution is not particularly limited, but since the undissolved matter causes nonuniformity, it is necessary to be careful not to cause the undissolved matter. For example, it can be dissolved by adding little by little while stirring with a propeller or wave rotor. At this time, heat may be applied if necessary. In addition, filtration of the dissolved aqueous solution may be performed. The concentration of the polymer aqueous solution is not particularly limited, but it is preferably about 0.5 to 2.0% by mass from the viewpoint of the undissolved matter. If the concentration is too low or too high, uniform adsorption will decrease.
　負極活物質である炭素材料に、作製したポリマー水溶液を添加し、ディスパー等を用いて撹拌する事で、ポリマーを吸着させる。この際、適宜純水を加えて、流動性を持たせる事が好ましい。十分に撹拌、分散させた後、炭素材料含有水溶液を恒温槽内に保持することで、乾燥させる。この際、温度は８０℃以下で行うことが好ましい。１００℃前後のような、水が沸騰する高温で処理すると吸着したポリマーの均一性が低下する恐れがあるため、好ましくない。 The prepared polymer aqueous solution is added to the carbon material which is a negative electrode active material, and the polymer is adsorbed by stirring using a disper or the like. At this time, it is preferable to appropriately add pure water to impart fluidity. After sufficiently stirring and dispersing, the carbon material-containing aqueous solution is dried by keeping it in a thermostat. At this time, the temperature is preferably 80 ° C. or less. Treatment at a high temperature at which water boils, such as around 100 ° C., is not preferable because the uniformity of the adsorbed polymer may be reduced.
　水分がある程度気化した段階で、高温や、真空下に保持する事で更に水分を飛ばす工程を加えても構わない。但し、ポリマーが分解するような高温は好ましくない。 After the water has been vaporized to a certain extent, a step of further discharging the water by holding it at high temperature or under vacuum may be added. However, high temperatures at which the polymer decomposes are not preferable.
　得られた負極材は、解砕することが好ましい。解砕は、一般的なリチウムイオン二次電池用黒鉛材料の方法であれば特に限定されない。別の手法として、負極合剤スラリーの調整時に、ポリマーを添加する方法を用いても構わない。事後吸着は製造プロセスとの整合性を確保する必要があるが、事前吸着の場合に比べて製造コストを小さくする事が出来るメリットがある。 The obtained negative electrode material is preferably crushed. Crushing is not particularly limited as long as it is a method of a general lithium ion secondary battery graphite material. As another method, a method of adding a polymer may be used when preparing the negative electrode mixture slurry. Although it is necessary to ensure the consistency with the manufacturing process, the subsequent adsorption has an advantage that the manufacturing cost can be reduced as compared with the case of the prior adsorption.
　負極１２の作製方法は、特に限定されるものではないが、例えば、負極活物質、増粘剤、水溶性バインダ、及び事後吸着の場合、ポリマーを、溶媒中にいれ、ボールミル、プラネタリーミキサー等の一般的な混錬分散方法を用いてよく混練分散して、負極合剤スラリーを作製する。続いて、この負極合剤スラリーを、塗布機を用いて銅等の金属箔からなる集電体上に塗布し、例えば１００℃前後の適当な温度にて真空乾燥し、プレス機を用いて圧縮成形した後に所望の大きさに切断又は打ち抜いて、目的の負極１２を作製することができる。 The method for producing the negative electrode 12 is not particularly limited. For example, the negative electrode active material, a thickener, a water-soluble binder, and in the case of post adsorption, the polymer is put in a solvent, a ball mill, a planetary mixer, etc. The mixture is well kneaded and dispersed using a general mixing and dispersing method of the above to prepare a negative electrode mixture slurry. Subsequently, this negative electrode mixture slurry is applied onto a current collector made of metal foil such as copper using a coating machine, vacuum dried at an appropriate temperature of, for example, around 100 ° C., and compressed using a press machine. After molding, it can be cut or punched into a desired size to produce the intended negative electrode 12.
　負極合剤スラリーを調製する際の溶媒としては、特に限定されないが、例えば、純水、Ｎ－メチル－２－ピロリドン（ＮＭＰ）、エチレングリコール、トルエン、キシレン等が挙げられる。 The solvent for preparing the negative electrode mixture slurry is not particularly limited, and examples thereof include pure water, N-methyl-2-pyrrolidone (NMP), ethylene glycol, toluene, xylene and the like.
　水溶性バインダとしては、アクリロニトリル－ブタジエンゴム（ＮＢＲ）やスチレン－ブタジエンゴム（ＳＢＲ）等の非フッ素系有機重合体を負極合剤に添加してもよい。更に増粘剤として、水溶性多糖類を併用する事が好ましい。水溶性多糖類としては、メチルセルロース、エチルセルロース、アセチルセルロース、ヒドロキシエチルセルロース、カルボキシメチルセルロース、でんぷん、カラギナン、プルラン、グアーガム、ザンサンガム（キサンタンガム）、ヒドロキシプロピルセルロース、ヒドロキシプロピルメチルセルロース等が挙げられる。これらのうち、一部を塩にしてもよい。この中では、特にカルボキシメチルセルロースのナトリウム塩が好ましい。これらの化合物は単独で使用してもよいし、２種以上を組み合わせて使用してもよい。 As the water soluble binder, a non-fluorinated organic polymer such as acrylonitrile-butadiene rubber (NBR) or styrene-butadiene rubber (SBR) may be added to the negative electrode mixture. Furthermore, it is preferable to use a water-soluble polysaccharide in combination as a thickener. Examples of water-soluble polysaccharides include methylcellulose, ethylcellulose, acetylcellulose, hydroxyethylcellulose, carboxymethylcellulose, starch, carrageenan, pullulan, guar gum, xanthan gum (xanthan gum), hydroxypropyl cellulose, hydroxypropyl methylcellulose and the like. Of these, some may be salted. Among these, sodium salt of carboxymethylcellulose is particularly preferable. These compounds may be used alone or in combination of two or more.
　負極１２の集電体には、厚さが１０～１００μｍの銅箔、厚さが１０～１００μｍで孔径０．１～１０ｍｍの銅製穿孔箔、エキスパンドメタル、又は発泡金属板等が用いられる。銅の他に、ステンレス、チタン、又はニッケル等の材質も適用可能である。本発明では、材質、形状、製造方法等に制限されることなく、任意の集電体を使用することができる。 For the current collector of the negative electrode 12, a copper foil having a thickness of 10 to 100 μm, a perforated copper foil having a thickness of 10 to 100 μm and a pore diameter of 0.1 to 10 mm, an expanded metal, a foam metal plate or the like is used. Besides copper, materials such as stainless steel, titanium or nickel are also applicable. In the present invention, any current collector can be used without being limited to the material, shape, manufacturing method and the like.
　負極活物質、バインダ、及び有機溶媒を混合した負極スラリーを、ドクターブレード法、ディッピング法、又はスプレー法等によって集電体へ付着させた後、有機溶媒を乾燥させ、ロールプレスによって加圧成形することにより、負極を作製することができる。また、塗布から乾燥までを複数回行うことにより、多層合剤層を集電体に形成させることも可能である。 A negative electrode slurry obtained by mixing a negative electrode active material, a binder, and an organic solvent is attached to a current collector by a doctor blade method, a dipping method, a spray method or the like, and then the organic solvent is dried and pressure-formed by a roll press Thus, the negative electrode can be manufactured. In addition, the multilayer mixture layer can be formed on the current collector by performing the process from application to drying a plurality of times.
　負極には、上記の黒鉛、非黒鉛炭素等とは別の活物質として、リチウムと合金を形成する材料又は金属間化合物を形成する材料が混合されていても良い。例えば、アルミニウム、シリコン、スズ等の金属及びこれらの合金、リチウム含有の遷移金属窒化物Ｌｉ(3-x)ＭxＮ、ケイ素の低級酸化物ＬｉxＳｉＯy（０≦ｘ、０＜ｙ＜２）、及びスズの低級酸化物ＬｉxＳｎＯy（０≦ｘ、０＜ｙ＜２）が挙げられる。上記の材料以外の材料が混合する材料として、選択しても構わない。 In the negative electrode, a material forming an alloy with lithium or a material forming an intermetallic compound may be mixed as an active material different from the above-mentioned graphite, non-graphite carbon and the like. For example, metals such as aluminum, silicon, tin and their alloys, lithium-containing transition metal nitride Li (3-x) M x N, lower oxides of silicon Li x SiO y (0 ≦ x, 0 <y < 2) and lower oxides of tin, Li x SnO y (0 ≦ x, 0 <y <2). You may select as a material which materials other than said material mix.
＜正極＞
　正極１０は、正極活物質、導電剤、バインダ、及び集電体から構成される。正極活物質を例示すると、ＬｉＣｏＯ2、ＬｉＮｉＯ2、及びＬｉＭｎ2Ｏ4が代表例である。他に、ＬｉＭｎＯ3、ＬｉＭｎ2Ｏ3、ＬｉＭｎＯ2、Ｌｉ4Ｍｎ5Ｏ12、ＬｉＭｎ2-xＭｘＯ2（ただし、Ｍ＝Ｃｏ、Ｎｉ、Ｆｅ、Ｃｒ、Ｚｎ、Ｔｉからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．２）、Ｌｉ2Ｍｎ3ＭＯ8（ただし、Ｍ＝Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎからなる群から選ばれる少なくとも１種）、Ｌｉ1-xＡxＭｎ2Ｏ4（ただし、Ａ＝Ｍｇ、Ｂ、Ａｌ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｒ、Ｚｎ、Ｃａからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．１）、ＬｉＮｉ1-xＭxＯ2（ただし、Ｍ＝Ｃｏ、Ｆｅ、Ｇａからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．２）、ＬｉＦｅＯ2、Ｆｅ2（ＳＯ4）3、ＬｉＣｏ1-xＭxＯ2（ただし、Ｍ＝Ｎｉ、Ｆｅ、Ｍｎからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．２）、ＬｉＮｉ1-xＭxＯ2（ただし、Ｍ＝Ｍｎ、Ｆｅ、Ｃｏ、Ａｌ、Ｇａ、Ｃａ、Ｍｇからなる群から選ばれる少なくとも１種、ｘ＝０．０１～０．２）、Ｆｅ（ＭｏＯ4）3、ＦｅＦ3、ＬｉＦｅＰＯ4、及びＬｉＭｎＰＯ4等を列挙することができる。 <Positive electrode>
The positive electrode 10 includes a positive electrode active material, a conductive agent, a binder, and a current collector. As a positive electrode active material, LiCoO 2 , LiNiO 2 , and LiMn 2 O 4 are representative examples. In addition, at least one selected from the group consisting of LiMnO 3 , LiMn 2 O 3 , LiMnO 2 , Li 4 Mn 5 O 12 , and LiMn 2-x MxO 2 (wherein M = Co, Ni, Fe, Cr, Zn, Ti) 1 type, x = 0.01 to 0.2), Li 2 Mn 3 MO 8 (wherein M = at least 1 type selected from the group consisting of Fe, Co, Ni, Cu, Zn), Li 1-x A x Mn 2 O 4 (wherein A = Mg, B, Al, Fe, Co, Ni, Cr, Zn, Ca, at least one member selected from the group consisting of x = 0.01 to 0.1), LiNi 1 -x M x O 2 (wherein M = at least one selected from the group consisting of Co, Fe and Ga, x = 0.01 to 0.2), LiFeO 2 , Fe 2 (SO 4 ) 3 , LiCo 1 -x M x O 2 (where little is selected from the group consisting of M = Ni, Fe, Mn Both one, x = 0.01 ~ 0.2), LiNi 1-x M x O 2 ( however, M = Mn, Fe, Co , Al, Ga, Ca, at least one selected from the group consisting of Mg , X (0.01 to 0.2), Fe (MoO 4 ) 3 , FeF 3 , LiFePO 4 , LiMnPO 4 and the like can be listed.
　正極活物質の粒径は、正極活物質、導電剤、及びバインダから形成される合剤層の厚さ以下になるように通常は規定される。正極活物質の粉末中に合剤層厚さ以上のサイズを有する粗粒がある場合、予めふるい分級や風流分級等により粗粒を除去し、合剤層厚さ以下の粒子を作製することが好ましい。 The particle size of the positive electrode active material is usually defined to be equal to or less than the thickness of the mixture layer formed from the positive electrode active material, the conductive agent, and the binder. When the powder of the positive electrode active material contains coarse particles having a size equal to or larger than the mixture layer thickness, the coarse particles are removed in advance by sieve classification, air flow classification, etc. to produce particles of the mixed layer thickness or less. preferable.
　また、正極活物質は、一般に酸化物系であるために電気抵抗が高いので、電気伝導性を補うための炭素粉末からなる導電剤を利用する。正極活物質及び導電剤はともに通常は粉末であるので、粉末にバインダを混合して、粉末同士を結合させると同時に集電体へ接着させることができる。 In addition, since the positive electrode active material is generally oxide-based and has high electrical resistance, a conductive agent made of carbon powder is used to compensate for the electrical conductivity. Since both the positive electrode active material and the conductive agent are usually powders, the powders can be mixed with a binder to bond the powders together and simultaneously adhere to the current collector.
　正極１０の集電体には、厚さが１０～１００μｍのアルミニウム箔、厚さが１０～１００μｍで孔径が０．１～１０ｍｍのアルミニウム製穿孔箔、エキスパンドメタル、又は発泡金属板等が用いられる。アルミニウムの他に、ステンレスやチタン等の材質も適用可能である。本発明では、材質、形状、製造方法等に制限されることなく、任意の集電体を使用することができる。 For the current collector of the positive electrode 10, an aluminum foil having a thickness of 10 to 100 μm, a perforated aluminum foil having a thickness of 10 to 100 μm and a hole diameter of 0.1 to 10 mm, an expanded metal, a foam metal plate or the like is used. . Besides aluminum, materials such as stainless steel and titanium are also applicable. In the present invention, any current collector can be used without being limited to the material, shape, manufacturing method and the like.
　正極活物質、導電剤、バインダ、及び有機溶媒を混合した正極スラリーを、ドクターブレード法、ディッピング法、又はスプレー法等によって集電体へ付着させた後、有機溶媒を乾燥させ、ロールプレスによって加圧成形することにより、正極１０を作製することができる。また、塗布から乾燥までを複数回行うことにより、複数の合剤層を集電体に積層化させることも可能である。 A positive electrode slurry obtained by mixing a positive electrode active material, a conductive agent, a binder, and an organic solvent is attached to a current collector by a doctor blade method, dipping method, spray method or the like, then the organic solvent is dried and added by a roll press. The positive electrode 10 can be manufactured by pressure molding. Moreover, it is also possible to laminate a plurality of mixture layers on the current collector by performing application to drying a plurality of times.
＜セパレータ＞
　以上の方法で作製した正極１０及び負極１２の間にセパレータ１１を挿入し、正極１０及び負極１２の短絡を防止する。セパレータ１１には、ポリエチレン、ポリプロピレン等からなるポリオレフィン系高分子シート、又はポリオレフィン系高分子と４フッ化ポリエチレンを代表とするフッ素系高分子シートを溶着させた２層構造等を使用することが可能である。電池温度が高くなったときにセパレータ１１が収縮しないように、セパレータ１１の表面にセラミックス及びバインダの混合物を薄層状に形成してもよい。これらのセパレータ１１は、電池の充放電時にリチウムイオンを透過させる必要があるため、一般に細孔径が０．０１～１０μｍ、気孔率が２０～９０％であれば、リチウムイオン二次電池に使用可能である <Separator>
The separator 11 is inserted between the positive electrode 10 and the negative electrode 12 manufactured by the above method, and a short circuit of the positive electrode 10 and the negative electrode 12 is prevented. For the separator 11, it is possible to use a polyolefin-based polymer sheet made of polyethylene, polypropylene or the like, or a two-layer structure in which a polyolefin-based polymer and a fluorine-based polymer sheet represented by polyethylene tetrafluoride are welded. It is. A mixture of ceramics and a binder may be formed in a thin layer on the surface of the separator 11 so that the separator 11 does not shrink when the battery temperature rises. Since these separators 11 need to transmit lithium ions at the time of charge and discharge of the battery, they can generally be used in lithium ion secondary batteries if the pore size is 0.01 to 10 μm and the porosity is 20 to 90%. Is
＜電解質＞
　本発明の一実施形態で使用可能な電解液の代表例として、エチレンカーボネートにジメチルカーボネート、ジエチルカーボネート、又はエチルメチルカーボネート等を混合した溶媒に、電解質として六フッ化リン酸リチウム（ＬｉＰＦ6）、又はホウフッ化リチウム（ＬｉＢＦ4）を溶解させた溶液がある。本発明は、溶媒や電解質の種類、溶媒の混合比に制限されることなく、他の電解液も利用可能である。 <Electrolyte>
Lithium hexafluorophosphate (LiPF 6 ) as an electrolyte in a solvent prepared by mixing ethylene carbonate with dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate or the like as a representative example of an electrolytic solution usable in one embodiment of the present invention, Alternatively, there is a solution in which lithium borofluoride (LiBF 4 ) is dissolved. The present invention is not limited to the type of solvent and electrolyte, and the mixing ratio of solvents, and other electrolytic solutions can also be used.
　なお、電解液に使用可能な非水溶媒の例としては、プロピレンカーボネート、エチレンカーボネート（ＥＣ）、ブチレンカーボネート、ビニレンカーボネート、γ－ブチロラクトン、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、メチルエチルカーボネート、１、２－ジメトキシエタン、２－メチルテトラヒドロフラン、ジメチルスルフォキシド、１、３－ジオキソラン、ホルムアミド、ジメチルホルムアミド、プロピオン酸メチル、プロピオン酸エチル、リン酸トリエステル、トリメトキシメタン、ジオキソラン、ジエチルエーテル、スルホラン、３－メチル－２－オキサゾリジノン、テトラヒドロフラン、１、２－ジエトキシエタン、クロルエチレンカーボネート、又はクロルプロピレンカーボネート等の非水溶媒がある。本発明の電池に内蔵される正極１０又は負極１２上で分解しなければ、これ以外の溶媒を用いてもよい。 Examples of nonaqueous solvents that can be used in the electrolyte include propylene carbonate, ethylene carbonate (EC), butylene carbonate, vinylene carbonate, γ-butyrolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate. 1,2-Dimethoxyethane, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, methyl propionate, ethyl propionate, phosphoric acid triester, trimethoxymethane, dioxolane, diethyl ether , Sulfolane, 3-methyl-2-oxazolidinone, tetrahydrofuran, 1,2-diethoxyethane, chloroethylene carbonate, or non-water such as chloropropylene carbonate There is a medium. Other solvents may be used as long as they do not decompose on the positive electrode 10 or the negative electrode 12 incorporated in the battery of the present invention.
　また、電解質の例としては、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＣｌＯ4、ＬｉＣＦ3ＳＯ3、ＬｉＣＦ3ＣＯ2、ＬｉＡｓＦ6、ＬｉＳｂＦ6、又はリチウムトリフルオロメタンスルホンイミドで代表されるリチウムのイミド塩等、多種類のリチウム塩がある。これらの塩を、上記の溶媒に溶解してできた非水電解液を電池用電解液として使用することができる。本実施形態に係る電池が有する正極１０及び負極１２上で分解しなければ、これ以外の電解質を用いてもよい。 In addition, examples of the electrolyte, LiPF 6, LiBF 4, LiClO 4, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, or imide salts such as lithium represented by lithium trifluoromethane sulfonimide, multi There is a kind of lithium salt. A non-aqueous electrolytic solution prepared by dissolving these salts in the above-mentioned solvent can be used as a battery electrolytic solution. An electrolyte other than this may be used as long as it does not decompose on the positive electrode 10 and the negative electrode 12 of the battery according to the present embodiment.
　固体高分子電解質（ポリマー電解質）を用いる場合には、ポリエチレンオキシド、ポリアクリロニトリル、ポリフッ化ビニリデン、ポリメタクリル酸メチル、ポリヘキサフルオロプロピレン、ポリエチレンオキサイド等のイオン伝導性ポリマーを電解質に用いることができる。これらの固体高分子電解質を用いた場合、セパレータ１１を省略することができる利点がある。 When a solid polymer electrolyte (polymer electrolyte) is used, an ion conductive polymer such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polyhexafluoropropylene, polyethylene oxide can be used as the electrolyte. When these solid polymer electrolytes are used, there is an advantage that the separator 11 can be omitted.
　さらに、イオン性液体を用いることができる。例えば、１－ｅｔｈｙｌ－３－ｍｅｔｈｙｌｉｍｉｄａｚｏｌｉｕｍ　ｔｅｔｒａｆｌｕｏｒｏｂｏｒａｔｅ（ＥＭＩ－ＢＦ４）、リチウム塩ＬｉＮ（ＳＯ2ＣＦ3）2（ＬｉＴＦＳＩ）とトリグライムとテトラグライムとの混合錯体、環状四級アンモニウム系陽イオン（Ｎ－ｍｅｔｈｙｌ－Ｎ－ｐｒｏｐｙｌｐｙｒｒｏｌｉｄｉｎｉｕｍが例示される。）、及びイミド系陰イオン（ｂｉｓ（ｆｌｕｏｒｏｓｕｌｆｏｎｙｌ）ｉｍｉｄｅが例示される。）より、正極１０及び負極１２にて分解しない組み合わせを選択して、本実施形態に係る電池に用いることができる。 In addition, ionic liquids can be used. For example, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4), a mixed complex of lithium salt LiN (SO 2 CF 3 ) 2 (LiTFSI) with triglyme and tetraglyme, cyclic quaternary ammonium type cation (N-methyl) According to the embodiment, a combination which does not decompose at the positive electrode 10 and the negative electrode 12 is selected from -N-propylpyrolidinium) and an imide type anion (bis (fluorosulfonyl) imide). It can be used for batteries.
　本発明の一実施形態に係るリチウムイオン二次電池は、例えば、上述のような負極と正極とをセパレータを介して対向して配置し、電解質を注入することによって製造することができる。本発明の一実施形態に係るリチウムイオン二次電池の構造は特に限定されないが、通常、正極及び負極とそれらを隔てるセパレータとを捲回して捲回式電極群にするか、又は正極、負極及びセパレータを積層させて積層型の電極群とすることができる。 The lithium ion secondary battery according to an embodiment of the present invention can be manufactured, for example, by arranging the negative electrode and the positive electrode as described above with the separator interposed therebetween and injecting the electrolyte. The structure of the lithium ion secondary battery according to one embodiment of the present invention is not particularly limited, but usually, the positive electrode and the negative electrode and the separator separating them are wound to form a wound electrode group, or the positive electrode, the negative electrode and The separators can be stacked to form a stacked electrode group.
　以下、実施例及び比較例を示して本発明をさらに詳細に説明する。なお、以下の実施例は一例であり、これらに限定されるものではない。 Hereinafter, the present invention will be described in more detail by showing Examples and Comparative Examples. The following embodiments are merely examples, and the present invention is not limited to these.
　負極活物質の合成手順を示す。まずオートクレーブを用いて，石炭系コールタールを４００℃で熱処理し生コークスを得た。この生コークスを粉砕した後，２８００℃にて不活性雰囲気中でカ焼を行い，炭素層間距離（ｄ002）が０.３３５ｎｍの炭素材料を得た。この炭素材料を分級機付きの衝撃破砕機を用いて粉砕し，３００メッシュの篩にて粗粉を除去して炭素粒子とした。その際の平均粒径は１６．６μｍで比表面積は５．８ｍ2／ｇであった。 The synthetic | combination procedure of a negative electrode active material is shown. First, coal-based coal tar was heat-treated at 400 ° C using an autoclave to obtain raw coke. The raw coke was pulverized and calcined at 2800 ° C. in an inert atmosphere to obtain a carbon material having a carbon interlayer distance (d 002 ) of 0.335 nm. The carbon material was crushed using an impact crusher with a classifier, and coarse particles were removed with a 300-mesh sieve to obtain carbon particles. The average particle diameter at that time was 16.6 μm and the specific surface area was 5.8 m 2 / g.
　この黒鉛にポリマーを吸着させた。吸着させる高分子には、ポリビニルスルホン酸Ｎａを用いた。水溶液濃度１．０質量％になるように純水にポリビニルスルホン酸Ｎａを添加し、ウエーブロータで８ｈ撹拌し溶液とした。 The polymer was adsorbed to the graphite. Polyvinyl sulfonate Na was used as the polymer to be adsorbed. Sodium polyvinyl sulfonate was added to pure water so that the concentration of the aqueous solution would be 1.0% by mass, and the solution was stirred for 8 h with a wave rotor to prepare a solution.
　前述した黒鉛粒子１００ｇに対し、ポリマーの固形分比が１質量％になるように、ポリビニルスルホン酸Ｎａ水溶液１００ｇを撹拌しながら添加した。装置は、プラネタリーミキサーを用い、回転速度２０ｒｐｍで混練分散した後、ディスパーを用い、５０００ｒｐｍで３ｈ撹拌し、スラリー化した。 With respect to 100 g of the graphite particles described above, 100 g of an aqueous solution of sodium polyvinyl sulfonate was added with stirring so that the solid content ratio of the polymer was 1% by mass. The apparatus knead and disperse at a rotational speed of 20 rpm using a planetary mixer, and then stirred for 3 h at 5000 rpm using a disper to make a slurry.
　得られたスラリーを８０℃で３ｈ保持して乾燥後、１００℃真空乾燥を４ｈ実施した。 The obtained slurry was held at 80 ° C. for 3 h for drying, and then 100 ° C. vacuum drying was performed for 4 h.
　得られた塊状黒鉛をミキサーで解砕し、目開き５０μｍの篩を用いて分級し、これをリチウムイオン二次電池用負極活物質とした。その際の平均粒径は１７．８μｍであり、比表面積は３．２ｍ2／ｇであった。 The obtained massive graphite was crushed with a mixer, and classified using a sieve with an aperture of 50 μm, and this was used as a negative electrode active material for a lithium ion secondary battery. The average particle diameter at that time was 17.8 μm, and the specific surface area was 3.2 m 2 / g.
　正極活物質の合成手順を示す。原料として酸化ニッケル，酸化マンガン，酸化コバルトを使用し，原子比でＮｉ：Ｍｎ：Ｃｏ比が１：１：１となるように秤量し，湿式粉砕機で粉砕混合した。次に，バインダとしてポリビニルアルコール（ＰＶＡ）を加えた粉砕混合粉を噴霧乾燥機で造粒した。得られた造粒粉末を高純度アルミナ容器に入れ，ＰＶＡを蒸発させるため６００℃で１２時間の仮焼成を行い，空冷後解砕した。さらに，解砕粉にＬｉ：遷移金属（Ｎｉ，Ｍｎ，Ｃｏ）の原子比が１：１：１ となるよう水酸化リチウム一水和物を添加し，充分混合した。この混合粉末を高純度アルミナ容器に入れて９００℃で６時間の本焼成を行った。得られた正極活物質をボールミルで解砕分級した。この正極活物質の平均粒径は６μｍであった。 The synthetic | combination procedure of a positive electrode active material is shown. Nickel oxide, manganese oxide and cobalt oxide were used as raw materials, weighed so that the atomic ratio of Ni: Mn: Co was 1: 1: 1, and pulverized and mixed by a wet crusher. Next, the pulverized and mixed powder to which polyvinyl alcohol (PVA) was added as a binder was granulated with a spray dryer. The obtained granulated powder was placed in a high purity alumina container, and calcined for 12 hours at 600 ° C. in order to evaporate PVA, and after air cooling, it was crushed. Furthermore, lithium hydroxide monohydrate was added to the crushed powder so that the atomic ratio of Li: transition metal (Ni, Mn, Co) would be 1: 1: 1, and thoroughly mixed. The mixed powder was placed in a high purity alumina container and subjected to main firing at 900 ° C. for 6 hours. The obtained positive electrode active material was crushed and classified in a ball mill. The average particle size of this positive electrode active material was 6 μm.
　本実施例の炭素材料における炭素００２面の面間隔ｄ002はリガク製Ｘ線回折装置ＲＵ２００Ｂを用いて測定した。Ｘ線源には、Ｃｕを用い回折確度はＳｉを用いて補正を行った。測定により得たピークをプロファイルフィッティングすることにより、ブラッグの式を用いて算出することが出来る。 The spacing d 002 of the carbon 002 plane in the carbon material of the present example was measured using a Rigaku X-ray diffractometer RU 200 B. Cu was used for the X-ray source, and the diffraction accuracy was corrected using Si. By profile fitting the peak obtained by the measurement, it can be calculated using Bragg's equation.
　実施例における材料の粒径（５０％Ｄ）は（株）堀場製作所製レーザ回折／散乱式粒度分布測定装置ＬＡ－９２０を用いて調べた。光源としては，Ｈｅ－Ｎｅレーザ１ｍＷを用い，炭素粒子の分散媒はイオン交換水に界面活性剤を２滴いれた物とした。予め５分以上超音波処理を行い，更に測定中も超音波処理を行って，凝集を防ぎつつ測定を行った。測定結果の累積５０％粒径（５０％Ｄ）を平均粒径とした。 The particle sizes (50% D) of the materials in the examples were examined using a laser diffraction / scattering particle size distribution analyzer LA-920 manufactured by Horiba, Ltd. As a light source, 1 mW of He—Ne laser was used, and a dispersion medium of carbon particles was prepared by adding two drops of surfactant to ion-exchanged water. Ultrasonication was performed in advance for 5 minutes or more, and ultrasonication was performed during the measurement to prevent aggregation. The cumulative 50% particle size (50% D) of the measurement results was taken as the average particle size.
　実施例におけるリチウムイオン二次電池の負極活物質である炭素材料の比表面積は，炭素材料を１２０℃で３時間真空乾燥した後，日本ベル株式会社製ＢＥＬＳＯＲＰ－ｍｉｎｉを用い，７７Ｋでの窒素吸着を用いて平衡時間３００秒で測定した吸着等温線をＢＥＴ法で解析し求めた。 The specific surface area of the carbon material which is the negative electrode active material of the lithium ion secondary battery in the example is as follows: After vacuum drying the carbon material at 120 ° C. for 3 hours, using BELSORP-mini manufactured by Nippon Bell Co., Ltd., nitrogen adsorption at 77 K The adsorption isotherm measured at an equilibration time of 300 seconds using was analyzed by BET method.
　本実施例における体積抵抗率は三菱化学製ロレスターＧＰ、ＭＣＰ-T６１０を用いて測定した。粉体抵抗は、圧力を１ｋＮごとに２０ｋＮまで測定した。 The volume resistivity in this example was measured using Mitsubishi Chemical Lorester GP, MCP-T610. The powder resistance measured the pressure to 20 kN every 1 kN.
　次に，リチウムイオン二次電池を作成した。まず，正極を作製した。正極活物質８５．０重量部に導電材として粉末状炭素とアセチレンブラックをそれぞれ７．０重量部と２．０重量部加え，あらかじめバインダとして６．０重量部のＰＶＤＦをＮＭＰに溶解した溶液を加えて，さらにプラネタリ－ミキサーで混合し正極合剤スラリーとした。このスラリーを塗布機で厚さ２０μｍのアルミニウム箔の両面に均一かつ均等に塗布した塗布後ロールプレス機により電極密度が２．５５ｇ／ccになるように圧縮成形し，正極とした。 Next, a lithium ion secondary battery was created. First, a positive electrode was prepared. A solution prepared by dissolving 7.0 parts by weight of powdered carbon and 2.0 parts by weight of acetylene black as a conductive material in 85.0 parts by weight of a positive electrode active material and 6.0 parts by weight of PVDF in NMP as a binder in advance. In addition, they were further mixed by a planetary mixer to form a positive electrode mixture slurry. The slurry was uniformly and uniformly coated on both sides of a 20 μm thick aluminum foil by a coating machine, and then compression molded by a roll press so that the electrode density was 2.55 g / cc, to obtain a positive electrode.
　次に，負極を作製した。負極活物質としての前記黒鉛９７．０重量部に、ＣＭＣ（カルボメチルセルロース）の１％水溶液の固形分１．５重量部相当量と、ＳＢＲの４０％水溶液の固形分１．５重量部相当量を加え、さらにプラネタリ－ミキサーで混合し負極合剤スラリーを調製した。このスラリーを、厚さ１０μｍの圧延銅箔からなる集電体の両面に塗布機で均一かつ均等に塗布した塗布後、ロールプレス機で圧縮成形し、負極とした。 Next, the negative electrode was produced. 97.0 parts by weight of the graphite as a negative electrode active material, equivalent to 1.5 parts by weight of solid content of a 1% aqueous solution of CMC (carbomethylcellulose), and equivalent to 1.5 parts by weight of solid content of a 40% aqueous solution of SBR The mixture was further mixed by a planetary mixer to prepare a negative electrode mixture slurry. The slurry was applied uniformly and evenly on both sides of a current collector made of rolled copper foil with a thickness of 10 μm by a coating machine, and then compression molded by a roll press to obtain a negative electrode.
　まず，正極と負極を所望の大きさに裁断し，未塗布部にそれぞれ集電タブを超音波溶接した。集電タブはそれぞれ正極にはアルミニウムのリード片，負極にはニッケルのリード片を用いた。その後，厚み３０μｍのセパレータを多孔性のポリエチレンフィルムで正極と負極に挟みながら捲回したこの捲回体を電池缶に挿入し，負極タブを電池缶の缶底に抵抗溶接により接続し，正極タブには正極蓋を超音波溶接により接続した。体積比がＥＣ，ＤＭＣ，ＤＥＣの体積比１：１：１の混合溶媒に１モル／リットルのＬｉＰＦ6を溶解させた電解液を注液し，その後，正極蓋を電池缶にかしめて密封し，リチウムイオン二次電池を得た。 First, the positive electrode and the negative electrode were cut into desired sizes, and the current collecting tabs were ultrasonically welded to the uncoated portions. The current collection tab used the lead piece of aluminum for positive electrodes, and used the lead piece of nickel for negative electrodes. Thereafter, this wound body obtained by winding a 30 μm thick separator while sandwiching a porous polyethylene film between the positive electrode and the negative electrode is inserted into the battery can, and the negative electrode tab is connected to the can bottom of the battery can by resistance welding. The positive electrode lid was connected by ultrasonic welding. An electrolyte prepared by dissolving 1 mol / liter of LiPF 6 in a mixed solvent of 1: 1, 1: 1 by volume ratio of EC, DMC, and DEC is injected, and then the positive electrode lid is crimped on a battery can and sealed. , Obtained a lithium ion secondary battery.
　まず，電池の直流抵抗（ＤＣＲ）を測定し、電池の出力密度を求めた。作製した電池を常温（２５℃）前後で０.３Ｃ相当の電流で４．１Ｖまで充電し，その後４．１Ｖで電流が０.０３Ｃになるまで定電圧充電を行った。３０分休止後に０.３Ｃ相当の定電流で２．７Ｖまで定電流放電を行った。これを４サイクル行い初期化し、４サイクル目の放電容量より電池重量辺りの容量密度ｍＡｈ／ｇを求めたさらに０．３Ｃで３．６Ｖまで定電流充電行った後，電流４ＣＡ，８ＣＡ，１２ＣＡ，１６ＣＡの電流値で１０秒間放電した。この時の電圧値を求めて，これを２.５Ｖまで外挿したときの限界電流から出力密度を求めた。結果を表１に示す。 First, the direct current resistance (DCR) of the battery was measured to determine the power density of the battery. The manufactured battery was charged to 4.1 V with a current corresponding to 0.3 C at around normal temperature (25 ° C.), and then constant-voltage charging was performed at 4.1 V until the current was 0.03 C. After 30 minutes of rest, constant current discharge was performed to 2.7 V with a constant current of 0.3 C equivalent. Four cycles are performed to initialize, and the capacity density mAh / g per battery weight is determined from the discharge capacity at the fourth cycle. Furthermore, constant current charge is performed to 3.6 V at 0.3 C, and then currents 4CA, 8CA, 12CA, It was discharged for 10 seconds at a current value of 16 CA. The voltage value at this time was determined, and the output density was determined from the limiting current when this was extrapolated to 2.5 V. The results are shown in Table 1.
　次に、２５℃で、５００回の充放電サイクルを行った。各サイクルにおいては、１Ｃ相当の電流で４．１Ｖまで充電し、その後４．１Ｖで電流が０．０３Ｃになるまで定電圧充電を行った。放電は、１Ｃ相当の電流で２．７Ｖまで放電した。充放電の間には休止を３０分行った。 Next, 500 charge and discharge cycles were performed at 25 ° C. In each cycle, charging was performed to 4.1 V with a current of 1 C, and then constant-voltage charging was performed at 4.1 V until the current was 0.03 C. The discharge was performed to 2.7 V with a current of 1 C. A rest was performed for 30 minutes between charge and discharge.
　次いで、サイクルさせた電池を信頼性試験として電池の圧潰試験を行った。充電電圧４．１Ｖ、充電時間２時間、制限電流８００ｍＡの定電圧・定電流充電を行い、電池の圧潰試験を行った。直径６ｍｍの円柱の丸棒を用いて、この丸棒が電池の外寸が最も長くなる方向に対して垂直になる方向から電池の中央部に押しつけて、電池の厚みが半分になるまで潰した。この際結果を変化無し，弁作動のみ，弁作動＋発煙，弁作動＋発煙＋発火に分類した。ここで弁作動のみとは安全弁が開いた状態，弁作動＋発煙は安全弁が開いて同時に気体が噴出した状態，弁作動＋発煙＋発火は気体が電池から噴出し，発火した状態である。また，各表では変化なしは「変化無し」，弁作動のみを「弁作動」，弁作動＋発煙を「発煙」，弁作動＋発煙＋発火を「発火」と記載した。結果を表１に示す。 The cells were then subjected to a crush test as a reliability test. The battery was subjected to a crushing test by performing constant voltage and constant current charging with a charging voltage of 4.1 V, a charging time of 2 hours, and a limiting current of 800 mA. Using a cylindrical round bar with a diameter of 6 mm, this round bar was pressed against the center of the cell from the direction perpendicular to the direction in which the outer dimensions of the cell were longest, and the cell was crushed to half its thickness . At this time, the results were classified as no change, valve operation only, valve operation + smoke generation, valve operation + smoke generation + ignition. Here, only the valve operation is the state where the safety valve is open, the valve operation + smoke is the state where the safety valve is open and the gas is spouted simultaneously, and the valve operation + smoke + ignition is the state that the gas spouts from the battery and it is ignited. In each table, no change is described as "no change", only valve operation as "valve operation", valve operation + smoke as "fume", and valve operation + smoke + ignition as "ignition". The results are shown in Table 1.
　また信頼性試験として過充電試験をしてから電池の圧潰試験を行った。充電電圧を４．３Ｖに変更した以外は上述の方法と同様の手順で行った。結果を表１に示す。 In addition, after the overcharge test as a reliability test, the battery crush test was performed. The procedure was the same as that described above except that the charging voltage was changed to 4.3 V. The results are shown in Table 1.
　ポリビニルスルホン酸Ｎａをポリビニルスルホン酸に変更したこと以外は、同様に行った。 It carried out similarly except having changed polyvinyl sulfonic acid Na into polyvinyl sulfonic acid.
　ポリビニルスルホン酸Ｎａの水溶液濃度を０．５質量％にし、黒鉛と混合する際の添加量を２００ｇにしたこと以外は、実施例１と同様に行った。 The same procedure as in Example 1 was carried out except that the aqueous solution concentration of polyvinyl sulfonic acid Na was made 0.5 mass%, and the addition amount at the time of mixing with graphite was made 200 g.
　ポリビニルスルホン酸Ｎａの水溶液濃度を２．０質量％にし、黒鉛と混合する際の添加量を５０ｇにしたこと以外は、実施例１と同様に行った。 The same procedure as in Example 1 was carried out except that the aqueous solution concentration of polyvinyl sulfonate Na was changed to 2.0% by mass, and the addition amount at the time of mixing with graphite was changed to 50 g.
　黒鉛に対するポリマーの添加量を、ポリマー固形分比を２質量％になるように、ポリビニルスルホン酸Ｎａと黒鉛とを混合する際の添加量を２００ｇにしたこと以外は、実施例１と同様に行った。 The same procedure as in Example 1 was carried out except that the amount of polymer added to graphite was 200 g in the case of mixing sodium polyvinyl sulfonate and graphite so that the polymer solid content ratio was 2% by mass. The
　炭素への処理をＣＶＤでＷＯ3を１００ｎｍつけたこと以外は、実施例１と同様に行った。 The treatment to carbon was performed in the same manner as in Example 1 except that WO 3 was added to 100 nm by CVD.
（比較例１）
　炭素への処理を行わなかったこと以外は実施例１と同様に行った。 (Comparative example 1)
It carried out like Example 1 except not having performed processing to carbon.
（比較例２）
　ポリスビニルスルホン酸Ｎａの水溶液濃度を１０質量％にし、黒鉛と混合する際の添加量を１０ｇにしたこと以外は、実施例１と同様に行った。 (Comparative example 2)
The same procedure as in Example 1 was carried out except that the aqueous solution concentration of sodium poly (vinyl sulfonate) was 10% by mass, and the addition amount at the time of mixing with graphite was 10 g.
（比較例３）
　ポリスビニルスルホン酸Ｎａの水溶液濃度を４．０質量％にし、黒鉛と混合する際の添加量を５０ｇにしたこと以外は、実施例１と同様に行った。 (Comparative example 3)
The same procedure as in Example 1 was carried out except that the aqueous solution concentration of sodium poly (vinyl sulfonate) was set to 4.0 mass%, and the amount added when mixing with graphite was set to 50 g.
（比較例４）
　ポリスビニルスルホン酸Ｎａの水溶液濃度を５．０質量％にし、黒鉛と混合する際の添加量を２０ｇにしたこと以外は、実施例１と同様に行った。 (Comparative example 4)
The same procedure as in Example 1 was carried out except that the aqueous solution concentration of sodium poly (vinyl sulfonate) was set to 5.0% by mass, and the addition amount at the time of mixing with graphite was set to 20 g.
（比較例５）
　ポリマーをポリビニルアルコールに変更したこと意外は、実施例１と同様に行った。 (Comparative example 5)
Unexpectedly, the polymer was changed to polyvinyl alcohol in the same manner as in Example 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１の実施例１－６と比較例１－４より、密度２．０ｇ／ｃｃにおける体積抵抗率が０．３２Ω・ｃｍ未満であるときは、圧潰試験の際に４．１Ｖおよび４．３Ｖで発煙や発火が見られたのに対し、密度２．０ｇ／ｃｃにおける体積抵抗率が０．３２Ω・ｃｍ以上では、圧潰試験の際に４．１Ｖおよび４．３Ｖで発火が見られなかったことから信頼性が向上していることは明らかである。また，実施例１－６と比較例５を比較すると，密度２．０ｇ／ｃｃにおける体積抵抗率が０．３２Ω・ｃｍ以上であっても、低密度から高密度へ変化した際の体積抵抗率の減少が大きい場合、ＤＣＲが急激に上昇し、出力密度が低下した。 From Example 1-6 and Comparative Example 1-4 in Table 1, when the volume resistivity at a density of 2.0 g / cc is less than 0.32 Ω · cm, 4.1 V and 4.3 V in the crushing test. Smoke and ignition were observed in the case, but when the volume resistivity at a density of 2.0 g / cc was 0.32 Ω · cm or more, no ignition was observed at 4.1 V and 4.3 V in the crushing test It is clear from this that the reliability is improved. Moreover, when Example 1-6 and Comparative Example 5 are compared, even if the volume resistivity at a density of 2.0 g / cc is 0.32 Ω · cm or more, the volume resistivity at the time of changing from low density to high density When the decrease of is large, the DCR rises sharply and the power density decreases.
　このように，本発明で提供したリチウムイオン二次電池は従来技術と比較して，電池抵抗の上昇を最小限にしつつ、サイクル劣化後の電池の信頼性が向上したリチウムイオン二次電池であることが確認された。
Thus, the lithium ion secondary battery provided by the present invention is a lithium ion secondary battery in which the reliability of the battery after cycle deterioration is improved while minimizing the increase in battery resistance as compared with the prior art. That was confirmed.
１０　正極
１１　セパレータ
１２　負極
１３　電池缶
１４　正極タブ
１５　負極タブ
１６　内蓋
１７　内圧開放弁
１８　ガスケット
１９　ＰＴＣ素子
２０　電池蓋
２１　軸芯 DESCRIPTION OF SYMBOLS 10 Positive electrode 11 Separator 12 Negative electrode 13 Battery can 14 Positive electrode tab 15 Negative electrode tab 16 Inner lid 17 Internal pressure release valve 18 Gasket 19 PTC element 20 Battery lid 21 Axial core

Claims (12)

  1. 　リチウムイオンを吸蔵・放出するリチウムイオン二次電池用負極活物質であって、
    　前記負極活物質は、炭素よりなる核材を有し、密度２．０ｇ／ｃｃにおける体積抵抗率が、０．３２Ω・ｃｍ以上で、かつ式（１）を満たし、
    　前記炭素は、Ｘ線回折装置測定により求められる炭素００２面の面間隔が０．３３４ｎｍ以上０．３３８ｎｍ以下であることを特徴とするリチウムイオン二次電池負極活物質。
    　式（１）： ｒ2≧０．１３× ｒ1
    式（１）において、ｒ2は、密度２．０ｇ／ｃｃにおける体積抵抗率、ｒ1は、密度１．２ｇ／ｃｃにおける体積抵抗率を表す。     A negative electrode active material for a lithium ion secondary battery, which absorbs and releases lithium ions, comprising:
    The negative electrode active material has a core material made of carbon, has a volume resistivity at a density of 2.0 g / cc of 0.32 Ω · cm or more, and satisfies the formula (1),
    The said carbon is a lithium ion secondary battery negative electrode active material characterized by the spacing of the carbon 002 plane calculated | required by X-ray-diffraction apparatus measurement being 0.334 nm-0.338 nm.
    Formula (1): r 2 0.10.13 × r 1
    In the formula (1), r 2 is the volume resistivity in the density of 2.0 g / cc, r 1 represents the volume resistivity at a density 1.2 g / cc.
  2. 　請求項１に記載のリチウムイオン二次電池用負極活物質であって、
    　前記負極活物質は、前記核材を被覆する被覆層を備えることを特徴とするリチウムイオン二次電池用負極活物質。     It is a negative electrode active material for lithium ion secondary batteries of Claim 1, Comprising:
    The said negative electrode active material is provided with the coating layer which coat | covers the said nuclear material, The negative electrode active material for lithium ion secondary batteries characterized by the above-mentioned.
  3. 　請求項２に記載のリチウムイオン二次電池用負極活物質であって、
    　前記被覆層は、ポリマーを有することを特徴とするリチウムイオン二次電池用負極活物質。     It is a negative electrode active material for lithium ion secondary batteries of Claim 2, Comprising:
    The said coating layer has a polymer, The negative electrode active material for lithium ion secondary batteries characterized by the above-mentioned.
  4. 　請求項３に記載のリチウムイオン二次電池用負極活物質において、
    　前記ポリマーは、スルホン酸基、スルホニル基、チオール基、スルフィド基の少なくともいずれかの官能基を有することを特徴とするリチウムイオン二次電池用負極活物質。     In the negative electrode active material for a lithium ion secondary battery according to claim 3,
    The said polymer has a functional group of at least one of a sulfonic acid group, a sulfonyl group, a thiol group, and a sulfide group, The negative electrode active material for lithium ion secondary batteries characterized by the above-mentioned.
  5. 　請求項４に記載のリチウムイオン二次電池用負極活物質において、
    　前記ポリマーは、ビニル基、スチレン基の少なくともいずれかを有するモノマーの重合体であることを特徴とするリチウムイオン二次電池用負極活物質。     In the negative electrode active material for a lithium ion secondary battery according to claim 4,
    The negative electrode active material for a lithium ion secondary battery, wherein the polymer is a polymer of a monomer having at least one of a vinyl group and a styrene group.
  6. 　請求項３に記載のリチウムイオン二次電池用負極活物質において、
    　前記ポリマーはポリビニルスルホン酸ナトリウムであることを特徴とするリチウムイオン二次電池用負極活物質。     In the negative electrode active material for a lithium ion secondary battery according to claim 3,
    The negative electrode active material for a lithium ion secondary battery, wherein the polymer is sodium polyvinyl sulfonate.
  7. 　請求項１ないし請求項６のいずれかに記載のリチウムイオン二次電池用負極活物質において、
    　前記負極活物質の粒径が３μｍ以上３０μｍ以下であることを特徴とするリチウムイオン二次電池用負極活物質。     In the negative electrode active material for a lithium ion secondary battery according to any one of claims 1 to 6,
    The particle diameter of the said negative electrode active material is 3 micrometers-30 micrometers, The negative electrode active material for lithium ion secondary batteries characterized by the above-mentioned.
  8. 　リチウムイオンを吸蔵・放出するリチウムイオン二次電池用負極活物質の製造方法であって、
    　前記負極活物質は、炭素よりなる核材と前記核材を被覆する被覆層とを有し、密度２．０ｇ／ｃｃにおける体積抵抗率が、０．３２Ω・ｃｍ以上で、式（１）を満たし、
    　前記炭素は、Ｘ線回折装置（ＸＲＤ）測定により求められる炭素００２面の面間隔が０．３３４ｎｍ以上０．３３８ｎｍ以下であり、
    　前記被覆層は、ポリマーを有し、
    　前記核材に前記ポリマーを添加する際の前記ポリマーの水溶液の濃度が０．５質量％以上２．０質量％以下であることを特徴とするリチウムイオン二次電池用負極活物質の製造方法。
    　式（１）： ｒ2≧０．１３× ｒ1
    式（１）において、ｒ2は、密度２．０ｇ／ｃｃにおける体積抵抗率、ｒ1は、密度１．２ｇ／ｃｃにおける体積抵抗率を表す。     A method for producing a negative electrode active material for a lithium ion secondary battery, which absorbs and releases lithium ions, comprising:
    The negative electrode active material has a core material made of carbon and a covering layer covering the core material, and the volume resistivity at a density of 2.0 g / cc is 0.32 Ω · cm or more, and the formula (1) Meet
    The carbon has a spacing of 0.334 nm to 0.338 nm between the carbon 002 planes determined by X-ray diffraction (XRD) measurement,
    The covering layer comprises a polymer,
    The method for producing a negative electrode active material for a lithium ion secondary battery, wherein the concentration of the aqueous solution of the polymer at the time of adding the polymer to the core material is 0.5% by mass or more and 2.0% by mass or less.
    Formula (1): r 2 0.10.13 × r 1
    In the formula (1), r 2 is the volume resistivity in the density of 2.0 g / cc, r 1 represents the volume resistivity at a density 1.2 g / cc.
  9. 　請求項３ないし請求項７のいずれかに記載のリチウムイオン二次電池用負極活物質の製造方法において、
    　濃度が０．５質量％以上２．０質量％以下である前記ポリマーの水溶液を調製する工程と、
    　前記核材に、前記ポリマーの水溶液を添加する工程と、
    　前記核材を含むポリマー水溶液を、８０℃以下で乾燥させる工程と、を含むリチウムイオン二次電池用負極活物質の製造方法。     In the method of manufacturing a negative electrode active material for a lithium ion secondary battery according to any one of claims 3 to 7,
    Preparing an aqueous solution of the polymer having a concentration of 0.5% by weight or more and 2.0% by weight or less;
    Adding an aqueous solution of the polymer to the core material;
    Drying the polymer aqueous solution containing the core material at 80 ° C. or less. A method for producing a negative electrode active material for a lithium ion secondary battery.
  10. 　請求項１ないし請求項７のいずれかに記載のリチウムイオン二次電池用負極活物質を用いたリチウムイオン二次電池用負極。 An anode for a lithium ion secondary battery using the anode active material for a lithium ion secondary battery according to any one of claims 1 to 7.
  11. 　請求項１０に記載のリチウムイオン二次電池用負極であって、
    　前記負極は負極活物質、負極集電体、バインダを有し、
    　前記バインダは水溶性であることを特徴とするリチウムイオン二次電池用負極。     It is a negative electrode for lithium ion secondary batteries of Claim 10, Comprising:
    The negative electrode includes a negative electrode active material, a negative electrode current collector, and a binder.
    The said binder is water-soluble, The negative electrode for lithium ion secondary batteries characterized by the above-mentioned.
  12. 　請求項１０または請求項１１に記載のリチウムイオン二次電池用負極を用いたリチウムイオン二次電池用電池。 The battery for lithium ion secondary batteries using the negative electrode for lithium ion secondary batteries of Claim 10 or Claim 11.
PCT/JP2013/051694 2013-01-28 2013-01-28 Negative electrode active material for lithium ion secondary cell, and lithium ion secondary cell obtained using same WO2014115322A1 (en)

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